China says it remains united with Russia in opposing foreign intervention in Syria's conflict, as Syria barred a number of U.S. and European diplomats on Tuesday.

With the Russian president visiting Beijing, Chinese foreign ministry spokesman Liu Weimin said the two countries oppose regime change by force in Syria, led for 11 years by President Bashar al-Assad. Liu was speaking as Russian President Vladimir Putin met with Chinese leaders including President Hu Jintao.

Liu said China and Russia continue to call for an immediate end to Syria's violence and the start of a political dialogue between the Assad government and the opposition. China and Russia have repeatedly blocked efforts by Western and Arab nations who are pushing for regime change and have put sanctions on the Syrian government and its leaders.

Damascus said Tuesday it is expelling diplomats of several nations in response to the recent expulsions of Syrian diplomats.

The Syrian government said its expulsion order includes the ambassadors and other staff of the United States, Britain, France and Turkey. Some of those diplomats already had been withdrawn from Syria in protest at the government's crackdown on the uprising.

The rebel Free Syrian Army said Monday it is no longer bound by an April cease-fire agreement that forms a key part of a U.N.-backed plan to resolve the Syrian crisis. Rebel spokesman Sami al-Kurdi told the Reuters news agency the FSA had resumed offensive operations “to defend our people.”

The Britain-based Syrian Observatory for Human Rights has said rebels have intensified attacks on government checkpoints in recent days.

International mediator Kofi Annan is due to brief the U.N. Security Council on the Syrian conflict on Thursday and will discuss the issue with U.S. Secretary of State Hillary Clinton in Washington on Friday.

Reuters reported Tuesday that the Assad government has agreed to allow the U.N. and international aid agencies to expand humanitarian operations in Syria.