Yara Bayoumy, Jonathan Landay & John Walcott Skeptics in the US government, European allies in the anti-Daesh (the so-called IS) coalition and the main Syrian opposition, distrustful of Russia's intentions, are questioning Secretary of State John Kerry's latest proposal for closer US-Russian cooperation against extremist groups in Syria. Several US military and intelligence officials called the plan naive, and said Kerry risks falling into a trap that Russian President Vladimir Putin has laid to discredit the United States with moderate rebel groups and drive some of their fighters into the arms of Daesh and other extremist groups. Some European members of the coalition against Daesh forces have expressed concern about sharing intelligence with Russia, which they say has been an untrustworthy partner in Syria. The current proposal, which Kerry hopes to conclude within weeks, envisions ways in which Washington and Moscow would share intelligence to coordinate air strikes against the Al-Qaeda-affiliated Nusra Front and prohibit the Syrian air force from attacking moderate rebel groups. Kerry's State Department and White House allies say the plan is the best chance to limit the fighting that is driving thousands of Syrians, mixed with some trained Daesh fighters, into exile in Europe and preventing humanitarian aid from reaching tens of thousands more, as well as preserving a political track. In the end, according to two officials who support Kerry's efforts, there is no alternative to working with the Russians. "There are reasons to be skeptical, as with any approach in Syria, but those who criticize this plan as unlikely to work or flawed on other grounds, like working with Russia, have the responsibility of presenting something better or more effective," said former White House Middle East adviser Philip Gordon, now with the Council on Foreign Relations think tank. Kerry's critics say the plan is flawed, in part because as it now stands it would leave the Russians and Syrians free to use ground troops and artillery against moderate groups fighting Syrian President Bashar Assad's forces. They also say targeting the Nusra Front is difficult because in some areas its fighters are comingled with more moderate rebels. "That underscores two basic problems that Kerry seems to be ignoring," said one US official, speaking on condition of anonymity. "One: The Russians' aim in Syria is still either keeping Assad in power or finding some successor who is acceptable to them. ... And two: Putin has proved over and over again, and not just in Syria, that he cannot be trusted to honor any agreement he makes if he decides it's no longer in Russia's interest." Kerry and his Russian counterpart, Sergei Lavrov, will have opportunities to meet within days in Geneva, Laos or both. But even if it is adopted, the plan is unlikely to provide quick relief for civilians trapped in a five-year-old civil war that the United Nations estimates has killed 400,000 people. Kerry told reporters on Friday that Obama had "authorized and ordered this track" and that the plan would be based on specific steps, not trust. But even Kerry has refrained from voicing optimism, instead saying the effort was showing "a modicum of promise." A European diplomat said Kerry and Lavrov have agreed to draft a map showing where the Nusra Front operates. "The two sides would then, through joint analysis, decide who to target ... by getting the US in the same tactical room; Moscow would then have to guarantee that Assad's planes stopped bombing," the diplomat said. "He is, in his Kerry way, optimistic. But the devil is in the details, and we're not convinced that Moscow is serious." British Defense Secretary Michael Fallon said the United States and Russia have an understanding to minimize the danger of aircraft interfering or colliding with each other, and that the British were covered by that understanding. "But it certainly does not extend to any cooperation over targeting, and we would not welcome that," Fallon said at an event in Washington. Many US officials are concerned that sharing intelligence with Russia could risk revealing US intelligence sources, methods and capabilities. Andrei Klimov, deputy chairman of the international affairs committee in Russia's upper house of parliament, said that even if the plan is agreed upon, it would be for only a short time, until the next US administration takes office. Obama's presidency ends in January. "I'm afraid Assad will expect tricks from the Americans," Klimov said. "They have been saying constantly he's an outcast ... and now they're about to tell Assad, ‘You know, please give us a day's advance notice before you want to trash someone with your forces.'" "Every time while talking to Assad we have to convince him, give arguments, additional guarantees. ... We can't give him orders, he's on his own soil." Following a meeting with Putin last week, Kerry expressed concern about indiscriminate bombings by Syrian forces, but did not mention Russian violations of a cessation of hostilities agreement, although the CIA publicly has pointed to them. "What's striking is not what Kerry has said, but what he's failed to say," said another US official, adding that Kerry had left out the "inconvenient facts" about Russian violations. Robert Ford, a former US ambassador to Syria and now a senior fellow at the Middle East Institute think tank in Washington, said that whether it was Moscow's bad intent or lack of leverage, "it's not clear to me that the Russians can deliver on their side of the deal." The Syrian opposition said it was concerned whether Russia could succeed in getting the Assad's government to ground its air force. "The (Obama) administration has put its bet on the good faith cooperation of the Russians, with so far very disappointing results," Basma Kodmani, a member of the main Syrian opposition High Negotiations Committee, said in Washington last week.