The agreement between US Secretary of State John Kerry and his Russian counterpart Sergei Lavrov, which offered a plan for the destruction of Syria's chemical weapons, came as a surprise that few thought possible.

The deal was the climax of a turbulent week that began in London with Kerry's remark that Syria's President Bashar al-Assad could still avoid a military attack if he handed over all his chemical weapons to international control "within a week." What Kerry possibly couldn't have believed himself now seems to have become possible, though the deadline has been extended to six months.

A breakthrough

"It's a breakthrough," Bruce Riedel, a Middle East expert at Washington think tank the Brookings Institution, told DW. And to Mark Jacobson, senior fellow at the German Marshall Fund, US President Barack Obama has succeeded in using diplomacy to prevent Syria from using chemical weapons again.

The analyst also argued that the president deserves credit for putting national and international security ahead of his own political interests. "The world should thank him for that," he said.

But plenty of questions still need to be answered. For instance, how will Assad, who has now been upgraded to negotiating partner, be made to answer for the deadly chemical weapons attack that many believe he ordered in August?

Success for Obama and Putin

Nevertheless, Riedel rates US-Russian cooperation on the destruction of Syria's chemical weapons as "a major success for Obama and Russian President Vladimir Putin, even if we know that implementing the agreement will be very difficult."

In its Saturday edition, the "Washington Post" reported that State Department officials in Kerry's delegation in Geneva estimate that more than one million kilos of weaponized chemical substances have been distributed to more than 45 different places in Syria.

While Riedel said the Russians and the Syrians are likely to hand over the required list of stockpiles punctually within a week, he added that the United Nations still face great difficulties. For one thing, he said, it's hard to imagine how they will be able to work in the middle of a bloody civil war. Assad will be required to guarantee the inspectors' safety. Some of the rebels, particularly those with al-Qaeda affiliations, could open fire on the inspectors.

"That's the hard part," said Riedel. "Putin may well be expecting such acts of sabotage. That would leave Assad suddenly looking reasonable and responsible."

UN back in the game

The deal between Kerry and Lavrov - aiming to hash out a joint UN resolution - puts the United Nations back in the peace process. Indeed, UN Secretary-General Ban Ki-moon welcomed the deal in Geneva just as much as the US president did.

And Obama, who was condemned as dithering and weak both at home and internationally, will claim that his strategy of forcing a diplomatic solution with the "credible threat of military force" has been vindicated. This comes despite the fact that Kerry had, rather meekly, ended up asking the representatives of the American people in Congress to approve an "unbelievably small" operation.

The received opinion in Washington is that Obama has avoided what would have been a devastating defeat in Congress on the question of using military force in Syria. "Obama was lucky in his pragmatism, and it was clever of him to take up Putin's offer - in spite of Edward Snowden and the other difficulties that have caused bad blood," said Riedel, referring to recent tension in the US-Russian relationship.

He said the president should postpone the congressional vote indefinitely. Even if the Geneva deal strengthens his hand, Obama will still struggle to get a majority in the Senate and the House of Representatives if it emerges that the Russians were bluffing - in other words, if Moscow vetos a Security Council resolution threatening Syria with military action for non-compliance.

European engagement

Jacobsen also said Congress is just as divided on the issue as America's European allies, and says that they too have responsibilities. The UN resolution will fail "if it is not shaped by the determination of the EU, NATO, and of course the Americans, to back up the agreement with military force."

So even if the present relief is palpable in European capitals from Berlin to London - without resolute European backing, it could all still collapse. That gives Kerry enough to talk about on his next trip to Europe.