US Secretary of State Hillary Clinton met Russian Foreign Minister Sergei Lavrov and UN peace envoy Lakhdar Brahimi on Thursday as world leaders desperately seek an end to the conflict in Syria.
Amid fears the 21-month conflict, which has already claimed some 40,000 lives, may take a gruesome new turn, the three diplomats held crisis talks on the sidelines of an international meeting in Dublin.
"We have been trying hard to work with Russia to stop the bloodshed in Syria and start a political transition," Clinton told reporters shortly before the talks.
"Events on the ground are accelerating and we see that in many different ways," she added.
The three-way talks took place on the sidelines of a meeting of the Organization for Security and Cooperation in Europe (OSCE).
They come amid growing concern that the regime of President Bashar al-Assad could be preparing to use chemical weapons as it battles opposition rebels seeking to oust the long-time leader.
US officials hope there may be a new willingness by Moscow, a staunch ally of Damascus, to probe ways to bring more pressure to bear on Assad to step down.
The United States has been calling for some time for Russia to use its leverage with Assad to try to open the way towards a political transition.
Moscow has repeatedly vetoed UN Security Council resolutions aiming to sanction the regime.
US Secretary of State Hillary Clinton waits on December 4 before speaking at the residence of the US ambassador to Belgium in Brussels. Clinton will meet Russian Foreign Minister Sergei Lavrov and UN peace envoy Lakhdar Brahimi on Thursday for talks on the conflict in Syria, a US official said.
But it did initially sign onto a peace plan crafted by Brahimi's predecessor, Kofi Annan, until it wavered in the face of imposing punitive UN action if Syria refused to implement the accord.
Clinton and Lavrov met first on Thursday morning for bilateral talks in which a US senior official said they agreed that "they both have a lot of respect of his (Brahimi's) mission and want to be supportive of it".
Clinton and Lavrov talked about how "extremely seriously we need to be in continuing to send messages about the red line and the unacceptability of the use of or loss of control of chemical weapons".
Clinton on Wednesday renewed Washington's vow to find ways to provide fresh support for the Syrian opposition, which has come together in a new body known as the Syrian National Coalition.
"Now that there is a new opposition formed, we are going to be doing what we can to support that opposition," she told reporters in Brussels, before flying to Ireland.
Washington has so far provided humanitarian aid to the rebels, but refused to arm the opposition amid fears of pouring weapons into an already volatile region, where anti-US militant groups are springing up.
Clinton also warned Damascus again that any use of chemical weapons against rebel forces was a clear red line that must not be crossed.
Russian Foreign Minister Sergei Lavrov arrives for a Foreign Affairs ministers meeting at the NATO Headquarters in Brussels on December 4. The United States has been calling for some time for Russia to use its leverage with Syria's Bashar al-Assad to try to persuade him to step down, and open the way towards a political transition.
"Our concerns are that an increasingly desperate Assad regime might turn to chemical weapons or might lose control of them to one of the many groups that are now operating within Syria," she told reporters after a NATO meeting.
But she again pressed the Assad regime to make "the decision to participate in a political transition, ending the violence against its own people".
"We hope that they do so because we believe, as you know, that their fall is inevitable. It's just a question of how many people will die until that date occurs," Clinton said.
Russian President Vladimir Putin met Turkish Prime Minister Recep Tayyip Erdogan in Istanbul on Monday on a trip focused on resolving sharp differences over the conflict.
Last month, Erdogan said Russia held the key to the Syrian conflict, and that if Moscow took a "positive" stance in the UN Security Council it could push another key Damascus ally, Iran, to review its policies.
It was unclear though whether there would be any change of position on the Russian side during Thursday's three-way talks.
The Dublin talks also come ahead of a key meeting of the Friends of the Syrian People in Marrakesh next week, which Clinton will attend.
It is likely the United States will move towards recognising the Syrian National Coalition as the legitimate representative of the Syrian people at the meeting, after France last month became the first Western nation to do so.