DUBLIN — A new round of diplomacy on the conflict in Syria will begin on Thursday afternoon when Lakhdar Brahimi, the United Nations special envoy, hosts an unusual three-way meeting with Secretary of State Hillary Rodham Clinton and the Russian foreign minister, Sergey V. Lavrov.
The session, which is being held on the margins of a meeting on European security, comes amid reports of heightened activity at Syria’s chemical weapons sites and signs that Russia may be shifting its position on a political transition in Syria.
“Secretary Clinton has accepted an invitation by U.N. Special Envoy Brahimi for a trilateral meeting on Syria this afternoon with Mr. Brahimi and Russian Foreign Minister Lavrov,” a senior State Department official said Thursday morning.
This is not the first time that American and Russian consultations have spurred hopes of a possible breakthrough. In June, Mrs. Clinton, Mr. Lavrov and the United Nations’s envoy on the Syrian crisis at the time, former United Nations Secretary General Kofi Annan, appeared to be close to an agreement that a transitional government should be established and that President Bashar al-Assad give up power.
But that seeming understanding quickly broke down, with American officials complaining privately that the Russian side had pulled back from the deal. A major sticking point, it later emerged, was the American insistence that the United Nations Security Council authorize steps to pressure Mr. Assad if he refused to go along under Chapter 7 of the United Nations Charter, which could be used to authorize tougher economic sanctions and, in theory, the use of force.
It remained to be seen if the new round of negotiations would be more successful.
On the one hand, the military situation on the ground appears to be shifting in the rebels’ favor. Some Russian officials reportedly no longer believe that Mr. Assad will succeed in holding on to power and may have a new interest in working out arrangements for a transition. The changing battlefield, some experts say, may have led to a softening of the Russian position.
A senior Turkish official said that after President Vladimir V. Putin of Russia and Prime Minister Recep Tayyip Erdogan of Turkey recently met in Istanbul that Moscow was “softening” its “political tone” and would look for ways of getting Mr. Assad to relinquish power.
On the other hand, it was possible that Mr. Lavrov had, in effect, merely agreed to meet so that Russia could maintain influence over the discussions on Syria and find out what exactly Mr. Brahimi was prepared to propose.
There were indications on Thursday that Russian officials see the positions of Washington and Moscow on Syria moving slightly closer.
Deputy Foreign Minister Gennady Gatilov of Russia expressed satisfaction in a Twitter message that the United States was moving to designate Al Nusra Front, a Syrian opposition group seen by American experts as linked to Al Qaeda, as an international terrorist organization.
The aim of the American move, which is expected soon, would be to isolate radical foes of the Assad government.
With the rebels making gains on the ground, American officials have been trying to ensure that military developments do not outpace political arrangements for a possible transition. American officials have hinted that the United States would upgrade relations with the Syria opposition, possibly to formal recognition, if the coalition made progress on a political structure by the time of a meeting of the so-called Friends of Syria in Morocco.
But emerging policy on the Al Nusra Front also acknowledges Russia’s longstanding argument that the Syrian opposition includes radical jihadists. Mr. Gatilov said that the American step “reflects understanding of the danger of escalating terrorist activity in Syria.”
A lawmaker with the dominant party, United Russia, told British legislators visiting Moscow that Russia saw Mr. Assad’s government struggling. “We think that the Syrian government should execute its functions,” he said, according to the Interfax news service. “But time shows that this task is beyond its strength.”
Dimitri K. Simes, a Russia expert the Center for the National Interest in Washington, said, based on conversations with top officials, that Russia has indeed softened its position in light of military setbacks for the Assad government, and it is now understood that neither Mr. Assad nor his close associates would take a central role in a new government.
However, he said Russia still wanted Iran to take part in negotiations about the transition. Iran’s presence, he said, would reassure Alawites, the Shiite Muslim minority of Mr. Assad and the core of the military, that they would be protected in the change of government.
