The United States is proposing a new UN Security Council resolution demanding an end to violence in Syria, first by government forces and then by opposition fighters.

Diplomats said the draft resolution, obtained by The Associated Press, would be discussed behind closed doors Tuesday by the five permanent council members — the U.S., Russia, China, Britain and France — and Morocco, the Arab representative on the council.

Russia and China have vetoed two council resolutions, saying they were unbalanced and only demanded that the government stop attacks, not the opposition.

The U.S. draft also condemns the continuing human rights violations by President Bashar al-Assad's government.

In Damascus, China's special envoy to Syria was expected to press authorities for a ceasefire to end the country's crisis Tuesday, even as Beijing remained firmly opposed to any foreign intervention.

Li Huaqing, a former Chinese ambassador to Syria, was scheduled to meet with government officials during his two-day visit. He wasn't expected to meet figures from the opposition seeking to overthrow the Assad regime.

At the same time, a top Russian diplomat says Moscow is remaining firm in its policy on the Syria crisis and urging the West to press the Syrian opposition to stop fighting Assad's regime.

'Convinced we are right'

Moscow last month joined China in blocking a UN Security Council resolution against Damascus and accused the West of fueling the conflict by backing the opposition.

Deputy Foreign Minister Sergei Ryabkov told reporters Tuesday that "we are deeply convinced that we are right" and that the opposition should be urged to renounce violence.

Germany's foreign minister said Monday that he hopes Russia will recognize that it is on "the wrong side of history" and rethink its stance on Syria now that Prime Minister Vladimir Putin has won Sunday's presidential election.

The Syrian regime agreed Monday to allow visits by two other prominent international emissaries it had previously rebuffed — former UN Secretary-General Kofi Annan, the new special envoy to Syria, and UN humanitarian chief Valerie Amos.

Annan is to reach Damascus on Saturday representing the UN and the Arab League. Amos is to arrive Wednesday and leave Friday.

Syria welcomes humanitarian chief

Amos said the aim of her visit is "to urge all sides to allow unhindered access for humanitarian relief workers so they can evacuate the wounded and deliver essential supplies."

In a message welcoming her visit, Syria said she would be able to visit "some areas" — making it unlikely she will see some of the areas hardest-hit by Assad's forces, such as the Baba Amr neighbourhood in Homs, which government forces took from rebels last week after a monthlong siege.

Activists say hundreds were killed in nearly four weeks of government shelling before troops seized the area. Syrian authorities have not allowed Red Cross aid teams to enter the area since then, despite assurances they would be able to. Activists accuse the regime of trying to hide the area's destruction.

The UN says more than 7,500 people have been killed since Syria's uprising started in March 2011 with protests calling for Assad's ouster. The protests have spread as Assad's forces have cracked down on dissent, and some in the opposition have taken up arms to defend themselves and attack government troops.

Activists put the death toll at more than 8,000.

McCain calls for airstrikes

Syrian refugees fleeing to neighbouring Lebanon say they feared they would be slaughtered in their own homes as government forces hunted down opponents in a brutal offensive against the opposition stronghold of Homs.

With world pressure at a peak in the boiling crisis, U.S. Sen. John McCain called for airstrikes against Syria. He said the United States has a moral and strategic obligation to force out Assad and his loyalists.

"The only realistic way to do so is with foreign airpower," McCain said from the Senate floor. "The United States should lead an international effort to protect key population centres in Syria, especially in the north, through airstrikes on Assad's forces."

Also Monday, the UN refugee agency said that as many as 2,000 Syrians crossed into Lebanon over the last two days to flee the violence in their country. In the Lebanese border village of Qaa, families with women with small children came carrying only plastic bags filled with a few belongings.

"We fled the shelling and the strikes," said Hassana Abu Firas. She came with two families who had fled government shelling of their town al-Qusair, about  22 kilometres away, on the Syrian side.