Syrian Foreign Minister Walid Mualem was to begin a two-day visit to China on Wednesday in the first bilateral high-level exchange since the cease-fire brokered by UN-Arab League envoy to Syria Kofi Annan took effect last week.

The Chinese Foreign Ministry on Tuesday announced that Mualem was invited by his counterpart Yang Jiechi. Sources said that he would arrive in Beijing on Tuesday night.

Mualem will discuss ways to enhance bilateral relations and Annan's mission, according to Syria's state-run news agency SANA.

The further implementation of Annan's six-point peace plan will be the priority of the talks, experts said. The announcement of Mualem's visit comes days after his meeting with Russian Foreign Minister Sergei Lavrov.

A five-member advance team of United Nations observers arrived in Damascus on Sunday to monitor the truce between government troops and rebels, one of the parts of Annan's plan.

On Saturday, the UN Security Council unanimously approved the observers' mission, the first legally-binding UN document since the outbreak of the crisis in the Middle East country in March 2011. The team will be backed by other batches of observers over the next monitoring period, and the total number of observers may eventually reach 250.

The mission had started setting up headquarters and reaching out to the Syrian government and the opposition to ensure that both sides understand the role of the mission, Annan's spokesman Ahmad Fawzi said on Monday.

Moroccan Colonel Ahmed Himmiche, the mission's chief, said on Tuesday that the mission is not an easy process, stressing that all concerned parties should coordinate their efforts toward the success of the mission.

UN chief Ban Ki-moon on Monday called on the Syrian government to "guarantee freedom of access, freedom of movement within the country" and the opposition to "fully cooperate".

China's consistent support for Annan's mediation efforts has been valued by Syria and the international community, China's Middle East Envoy Wu Sike told China Daily.

"But since the cease-fire is still fragile, China will continue communicating with the government and oppositional parties, urging them to consolidate the cease-fire, cooperate with the UN's monitoring and conduct political dialogues," he said.

Sporadic violence has been reported across Syria during the truce. On Monday, at least nine people, including two officers, were killed in separate incidents, SANA said.

"Much of Syria is quieter ... We want to see a political process begin, but if violence is renewed ... then we're going to have to get back to planning what our next steps are," US Secretary of State Hillary Clinton said on Monday.

Russia on Tuesday called the cease-fire in Syria "fragile" and urged countries to put more pressure on the armed opposition to cooperate with Annan's peace plan.

The external forces who are interested in the failure of Annan's plan "are doing this by delivering arms to the Syrian opposition and stimulating the activity of rebels who continue to attack both government facilities and ... civilian facilities on a daily basis", Lavrov said in televised remarks, without naming specific countries.

"The Syrian government and the opposition parties have to proceed with the rest of Annan's six-point peace plan, including starting inclusive political dialogues, as soon as possible," said Li Guofu, director of Middle East studies with the China Institute of International Studies.

However, the biggest obstacle undermining Annan's efforts are the forces calling for Syrian President Bashar al-Assad to step down as a precondition to political dialogues, he said.

China will continue to play a constructive role in the Syria issue and urge concerned parties to carry out Annan's plan, though it's not an easy task for Assad to maintain the truce and guarantee the UN observers' safety, he added.

Xinhua and AFP contributed to this story.