(CNN) -- Russia and China voiced their strong opposition to international intervention or efforts to change the regime in Syria on Wednesday, as Russian President Vladimir Putin visited Beijing.
"Both sides firmly oppose any attempt to resolve the Syrian crisis through foreign military intervention as well as promoting forced 'regime change' at U.N. Security Council and other venues," a statement from Putin and Chinese counterpart Hu Jintao said.
The joint statement comes as leaders in the European Union and United States seek to ratchet up the pressure on Syrian President Bashar al-Assad and bring an end to 15 months of violence.
But world powers remain divided on how to tackle the thorny issue.
Meanwhile, opposition groups reported another 42 civilians killed in shelling and clashes Wednesday.
In their statement, Hu and Putin stressed the need for a domestic political solution to Syria's crisis.
"We firmly believe that the Syrian crisis has to be resolved fairly and peacefully by having all parties in conflict stop violence and start comprehensive political dialogue without foreign interference," it said.
"Both sides call on the Syrian government to start political dialogue with all opposition groups as soon as possible, make an effort in promoting the normalization of the Syrian situation, and restore domestic security as well as law and order in Syria."
The two leaders also reasserted their support for the six-point peace plan negotiated by Kofi Annan, the joint envoy to Syria for the United Nations and the Arab League.
Russia and China have previously used their veto power to block passage of U.N. resolutions condemning al-Assad's regime. Both countries have major trade deals with Syria.
White House Spokesman Jay Carney said the United States had been very clear on the need for Russia to play a "constructive role" in bringing about a political transition in Syria.
He added, "All options with regards to Syria are being discussed, and the need to take urgent action ... is very much on the minds of policymakers in the administration and at the United Nations and elsewhere."
Members of the international Friends of Syria group vowed Wednesday to keep stepping up pressure on the al-Assad regime after meeting in Washington to discuss imposing tougher sanctions.
"We have taken important steps, but much work remains," the group said in a statement. "We must continue to close off the regime's economic lifelines, expand the circle of countries vigorously implementing sanctions, and prevent the Syrian government from evading them."
Addressing the meeting, U.S. Treasury Secretary Tim Geithner said such sanctions could play an important role in hastening political change.
"Strong sanctions, effectively implemented, aggressively enforced, can help deprive the Syrian regime of the resources it needs to sustain itself and to continue its repression of the Syrian people," he said.
"Strong sanctions make clear to the Syrian business community and other supporters of the regime that their future is bleak so long as the Assad regime remains in power. And strong sanctions can help hasten the day the Assad regime relinquishes power."
In a public speech Sunday, al-Assad cited recent parliamentary elections as proof that his country is progressing.
And state-run media reported Wednesday that al-Assad has tasked an official with "the formation of a new government," though it was not clear whether the move would bring about any significant change.
Riyad Farid Hijab, who has been agriculture minister since April, was chosen for the assignment, the state-run Syrian Arab News Agency reported.
In recent months, the Syrian regime has touted what it calls "political reforms" in light of a yearlong uprising that has spawned international condemnation of the government's bloody crackdown on dissidents. Yet relentless reports of brutality and killings at the hands of the regime suggest that the Syrian crisis is far from over.
French Foreign Ministry spokesman Bernard Valero described al-Assad as "stubbornly deaf to the demands of his people" and dismissed the appointment of Hijab as "another masquerade, which does not meet the expectations of the Syrians and the international community."
He called on the Syrian regime to "stop killing its people and commit to implementing the plan of Mr. Kofi Annan."
The United States, meanwhile, is sending a delegation to Russia this week to press for tough action against the Syrian regime, led by special adviser Frederic Hof, a senior Obama administration official said Tuesday. The official was not authorized to speak on the record.
Annan is expected to discuss developments in Syria with U.S. Secretary of State Hillary Clinton in Washington this week.
Wednesday's 42 civilian deaths included 10 in Homs province, nine in Latakia province and eight in Hama, the opposition Local Coordination Committees of Syria said. There were also deaths in Deir Ezzor, Idlib province, Aleppo province, the Damascus suburbs and Daraa, the group said.
Intense shelling from tanks targeted a residential area in the Damascus suburbs, the Local Coordination Committees said earlier, while heavy shelling, powerful explosions and heavy gunfire also tormented the anti-government bastion of Homs. Meanwhile, U.N. observers near Hisn Citadel, in Homs province, were fired on from a checkpoint, making them reluctant to inspect the area, the Local Coordination Committees said.
The city of Hiffa, in Latakia province, suffered a second day of intense shelling and clashes, opposition activists said.
Regime forces tried to storm Hiffa again Wednesday, after fierce fighting Tuesday, the Local Coordination Committees and London-based Syrian Observatory for Human Rights said.
Rami Abdurrahman, of the Observatory, said initial information suggested that dozens of members of the regime forces had been injured in the latest fighting in the city and its outskirts. Roads leading to and from the city have been closed off, and shelling appears to be targeting them, the group said.
Despite the incessant turmoil, the Syrian government said it will let the United Nations enter the country and deliver humanitarian aid to people in need.
"After a long time of very intense negotiations, we now have an agreement in writing with the Syrian government on the scale, scope and modality of humanitarian action in Syria," said John Ging, director of operations at the U.N. Office for the Coordination of Humanitarian Affairs.
"Whether it's a breakthrough or not will depend on the action on the ground. I cannot predict what that will be, but we will work very hard to make it a breakthrough, because the people of Syria need us to break through with a much bigger humanitarian response."
Ging said Tuesday that the Syrian government has signed a memorandum that describes the planned humanitarian response for the approximately 1 million people who urgently need aid.
Syria also announced that it was expelling diplomats from 11 countries. The tit-for-tat move came a week after those nations expelled Syrian officials in response to a gruesome massacre in the town of Houla.
Syria's Foreign Ministry said diplomats from the United States, Britain, Switzerland, Turkey, France, Italy, Spain, Belgium, Bulgaria, Germany and Canada were being declared persona non grata.
Among them is U.S. Ambassador Robert Ford, who has been in the United States since February, when the U.S. government closed its embassy in Damascus.
But a U.S. official said Ford will keep working. "This certainly isn't going to stop Ambassador Ford from continuing his important outreach to the Syrian people," deputy State Department spokesman Mark Toner said in Washington. "He's going to continue our efforts to support a peaceful political transition for which the Syrian people have so bravely fought."
Residents of Houla, where at least 108 people were killed -- almost half of them children -- pleaded via Skype for basic necessities.
"For more than 10 days now, the criminal regime forces have cut off basic food items from entering Houla area," the statement from the opposition Houla Media Center said.
"They stopped flour, gas and medicine from coming in, and they continue to cut off electricity because the main supplying plant was hit by the sporadic shelling," the group said. "We call on relief and human rights organizations to help us and open humanitarian corridors for basic items so you do not become collaborators in the (regime's) massacres."
Al-Assad's regime denies responsibility for the massacre and has said it is fighting to stop "armed terrorist groups," the same vaguely defined entities it has blamed throughout the 15-month crisis.
Opposition activists and residents have said pro-regime forces shelled the city before going house to house, lining up residents and shooting them.
The United Nations says more than 9,000 people have been killed since the Syrian crisis began in March 2011. Opposition activists put the toll higher, with estimates of at least 12,000 to 14,000.