By Francois Murphy and David Brunnstrom
VIENNA (Reuters) - The United States, Russia and powers from the Middle East and Europe outlined a plan on Saturday for a political process in Syria leading to elections within two years, but differences over the fate of President Bashar al-Assad remained.
A day after gunmen and suicide bombers went on a rampage through Paris, killing at least 127 people, foreign ministers and senior officials from more than a dozen countries agreed to seek a ceasefire, but U.S. Secretary of State John Kerry said it would not apply to Islamic State.
French President Francois Hollande pledged a "merciless response" to the attacks, which he said had been organized by Islamic State. France is part of the U.S.-led coalition carrying out air strikes against Islamic State in Syria and Iraq.
Speaking in French after Saturday's talks, which began with a minute's silence for the victims in Paris, Kerry told a joint news conference with his Russian counterpart that the attacks only strengthened his country's resolve to fight terrorism.
"The impact of the war bleeds into all of our nations," Kerry said. "It is time for the bleeding in Syria to stop."
The Paris attacks shifted the focus of negotiations in Vienna from the detail of which organizations would count as opposition groups rather than terrorist ones, and could therefore take part in a political solution in Syria, to defeating Islamic State militarily.
Russia and the United States also seemed to turn a blind eye to their long-standing disagreement over Assad's fate. The West and its allies say he must leave office, while his allies Moscow and Tehran support elections in which he could stand.
"We still differ, obviously, on the issue of what happens with Bashar al-Assad," Kerry said. "But we are relying on the political process itself, led by Syrians, which it will be going forward, and the Syrians negotiating with Syrians; that that can help bring a close to this terrible chapter."
In a joint statement, the countries involved in the talks - including Saudi Arabia, Iran, Turkey and the five permanent members of the U.N. Security Council - laid out a plan including formal talks between the government and opposition by Jan. 1.
The statement did not make clear how those groups would be chosen. An agreement on lists of political organizations and terrorist groups has consistently eluded negotiators.
The participants in the talks also pledged to "take all possible steps" to ensure they and the groups they support adhere to a ceasefire in Syria, where 250,000 people have been killed in the civil war.
"(The countries) affirmed their support for a ceasefire ... and for a Syrian-led process that will, within a target of six months, establish credible, inclusive and non-sectarian governance, and set a schedule and process for drafting a new constitution," the statement said.
Russian Foreign Minister Sergei Lavrov said most but not all countries at the talks were in favor of an immediate truce.
"The participants expect to meet in approximately one month in order to review progress toward implementation of a ceasefire and the beginning of the political process," the joint statement said.
It also provided for elections based on a new constitution and supervised by the U.N. "within 18 months", without specifying exactly when from.
(Additional reporting by John Irish, Karin Strohecker and Vladimir Soldatkin; Editing by Hugh Lawson)