Backers of the Syrian uprising meet in Amman on Wednesday to discuss a US-Russian proposal for peace talks, as the brutal two-year conflict escalates close to the border with Lebanon.

"This meeting... in Amman is to bring together all of the key players in the region as well as the key partners in Europe and the United States to talk about strategy," a senior US State Department official said.

Eleven top diplomats from Britain, Egypt, France, Germany, Italy, Jordan, Qatar, Saudi Arabia, Turkey, the United Arab Emirates and the United States are attending the meeting of the so-called Friends of Syria group.

"It's basically to review where we are on Syria," the official said.

Ahead of the meeting, US Secretary of State John Kerry will hold a news conference at around 1130 GMT.

Jordan's Foreign Minister Nasser Judeh told reporters that the US-Russian deal was a "turning point" in the conflict, while Syria's ambassador to Jordan, Bahjat Suleiman, was to also hold a rare press conference at around 0900 GMT.

Earlier this month, the United States and Russia, which back opposite sides in the Syrian conflict, proposed a peace conference dubbed Geneva 2 to bring together rebels and representatives of President Bashar al-Assad's regime.

The US official described the proposed conference as "the most serious effort in the last two years to get the Syrian government to sit down and negotiate with the Syrian opposition...

"In my experience we haven't seen a push that has such clear support from the Russians, from the United Nations," he said.

A French diplomatic source said the proposed Geneva conference "comes at a time when the regime is taking the lead on the ground as its supporters are getting more and more involved."

But while the regime has reportedly already proposed the names of several potential envoys to the mooted conference, the opposition has yet to decide whether it will attend.

Syria's umbrella opposition National Coalition is reportedly not attending the Friends of Syria conference, but will be meeting this week in Istanbul, where it is expected to hammer out its stance on the peace effort.

The group will also be taking decisions on its leadership, in a move that officials say is key.

"One of the things we'll be talking about here in Amman... is what else needs to be done with respect to the military balance on the ground," the US official said, urging the opposition to unify ranks.

"The first thing to do is for the Syrian opposition coalition -- which we and Friends of Syria have all recognised as the legitimate representative of the Syrian people -- we need that opposition coalition to resolve its leadership questions and then turn to address its stance on Geneva. First things first," he said.

The diplomatic discussion comes against the backdrop of a major push by Syrian regime forces to retake the rebel stronghold of Qusayr in central Homs province bordering Lebanon.

The battle for the town, which lies between Damascus and the Mediterranean coast, is drawing in neighbouring Lebanon, with the country's powerful Shiite movement Hezbollah dispatching its fighters to bolster regime troops.

Sunni fighters from Lebanon are also reportedly joining the battle, fighting alongside Syrian rebels, though in smaller numbers than their Hezbollah counterparts.

The battle has raised tensions in the Sunni-majority Lebanese town of Tripoli, home to a minority of Alawites, the Shiite offshoot to which Assad belongs.

As the Qusayr offensive began on Sunday, clashes erupted in the northern Lebanese city of Tripoli. At least six people have died since then.

On Tuesday, the Syrian Observatory for Human Rights said over 100 people had been killed in the fighting in Qusayr since the assault started, including 31 Hezbollah fighters, 70 rebels and nine soldiers.

The group says a total of over 90,000 people have been killed since the Syria conflict began in March 2011.

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