If anyone saw last week’s US-Russian agreement to convene a peace conference on Syria as a potential breakthrough, Western leaders have been going out of their way to disabuse them.

International envoy Lakhdar Brahimi hailed the plan as the “first hopeful news” on Syria in a long time and deferred his own plans to resign after nine months of futile mediation.

He called the proposal “only a first step.” But even its sponsors are dampening expectations that a civil war estimated to have killed well over 70,000 can be doused soon, and pitfalls they cite in public are only a few of those lying in wait. “I’m not promising that it’s going to be successful,” US President Barack Obama said on Monday. Obstacles, he said, include Iran and Hezbollah, both of which support President Bashar Assad, as well as the Al-Qaeda-linked Al-Nusra Front on the opposition side.

Obama did not mention chronic disunity in the ranks of the Western-backed opposition or its almost complete lack of control over the now mostly Islamist insurgent forces on the ground. Once “the furies have been unleashed ... it’s very hard to put things back together,” he said.

The United States and Russia share interests in Middle Eastern stability and in curbing militancy, but remain far apart on how to pacify Syria and shape its political future.

On Tuesday, Russian President Vladimir Putin, who opposes foreign military intervention or arming the fighters, said after talks with Israeli Prime Minister Benjamin Netanyahu: “It is extremely important to avoid any actions that could aggravate the situation.” Israel, pursuing a campaign against Iran and Hezbollah, bombed targets near Damascus this month — part of a range of regional conflicts that are complicating and fueling the Syrian war; some of them have strong sectarian overtones.

Moscow, which has shielded Assad diplomatically since mostly secular peaceful protests against him erupted in March 2011, has long echoed the Syrian leader’s line that what later turned into an armed revolt is the work of foreign-backed militants.

Russia says Assad’s survival in power is not its goal, but insists his removal must not be a precondition for talks. Tentative cooperation between Washington and Moscow might help — Brahimi’s predecessor Kofi Annan quit last year in frustration at the diplomatic paralysis caused by big power divisions — but even acting in concert they might be impotent to staunch a conflict already spilling over to Syria’s neighbors.

It remains to be seen if they can cajole their deeply skeptical Syrian allies into joining the Geneva negotiations, whose earliest timing has now slipped from May to early June. The main opposition coalition, backed by Western and some Arab states, meets in Istanbul on May 23 to decide its stance. Previously it has demanded Assad’s exit before any talks, but Washington now seems ready to leave his future to negotiations.

Assad himself, buoyed by military gains against opposition strongholds in recent weeks, seems determined to cling to power.

On the battlefield, both sides have seen gains and reverses in recent weeks; fighters including the Al-Nusra Front counter-attacked east of Damascus to retake a town that served as a conduit for arms from Jordan into the capital before it was seized by government forces last month, rebel sources said.

The fighters’ struggle to end four decades of Assad family rule has been complicated in part by internal divisions along ideological and political lines, but in a rare move, brigades operating in Ghouta, a largely agricultural region on the eastern outskirts of Damascus, united under one command.

“With God’s will this will be a decisive battle in rural Damascus that will stop the advance of the regime army and reopen the supply route,” said one commander.

Information Minister Amran Zoabi said Assad’s leadership role was a decision “only for the Syrian people and the ballot box.” He said Syria wants specifics on the Geneva talks before deciding whether to attend.

US Secretary of State John Kerry said staying away would be “another one of President Assad’s gross miscalculations,” but added: “I don’t believe that that is the case at this moment. The Russians, Foreign Minister Sergey Lavrov has already given him the names of people who will negotiate.” Western powers want to step up pressure on Assad to hasten his fall, but have no appetite for the huge risks and costs of direct military intervention and have stopped short of arming fractured opposition factions, who have struggled to make headway.