CRITICS accuse Barack Obama of dithering in response to the spreading civil war in Syria. Officials in Washington say that, on the contrary, the president has been perfectly decisive—in refusing to get too deeply involved. Mr Obama believes that for all its horrors and rising death tolls, the fight between rebels and Syria’s president, Bashar Assad, is a stalemate: neither side can vanquish the other militarily. Only a political settlement uniting Syria’s rival parties and religious factions can bring lasting peace, thinks Mr Obama. This is why America is providing only what he calls “careful, calibrated” aid to the rebels, and will not be rushed into a fresh Middle East war, especially one with the potential to turn into a wider sectarian struggle between Sunni and Shia Muslims.

It was in that spirit of caution that the administration announced on June 13th that, for the first time, it would give weapons and other forms of lethal military kit to the rebels. Though the move met with bluster from Mr Assad’s ally, Russia—and wary enthusiasm from Syrian rebel commanders—it was not a giant step.

American officials have given scant detail, but it is thought that the CIA will co-ordinate the supply of light arms to the rebels. In an interview with PBS television on June 17th, Mr Obama derided the idea that heavier weapons, such as anti-tank or anti-helicopter rockets and missiles, could swiftly tip the balance of power away from the Assad regime. The new weaponry will be channelled through the Supreme Military Command, a Western-backed rebel body headed by Selim Idriss, a general who defected from Mr Assad’s forces, and whose connections to moderate groups America has been testing with supplies of food and medicine. America’s programme, likely to be based in Jordan, on Syria’s southern border, may in effect amount to a beefing up of a Saudi operation there, which already involves the CIA in training vetted rebels.

The official explanation for the decision to start arming the opposition rests on a recent assessment by American intelligence agencies, after weeks of investigations, that the Assad regime has used chemical weapons, including the nerve agent sarin, in several small-scale attacks on the opposition, killing as many as 150 people.

However, Obama aides have also linked the new policy to a “deteriorating situation” on the ground in Syria in recent weeks, as the regime enjoyed greater success on the battlefield, in part thanks to help from Iran and Hizbullah, Lebanon’s Shia party-cum-militia, which the United States regards as a terrorist outfit.

A question-mark hangs over what America hopes to achieve. Washington sources say that—having warned Syria publicly that the systematic use of chemical weapons would cross a “red line” and force America to change its policy—Mr Obama had to do something, on the grounds that superpowers do not bluff. In addition, advocates of arming the opposition have long argued that America may gain leverage by sending its own weaponry down supply-lines already filled with aid from Gulf Arab countries and Turkey. But without supplying anti-aircraft weapons, America is unlikely to give a boost to the rebels of the magnitude that Hizbullah gifted the regime when it helped Mr Assad’s army to capture the rebel stronghold of Qusayr on June 5th.

Some reckon it is even too late to achieve the more modest goals of bringing the fissiparous rebel groups under a single command structure and marginalising more extreme elements, in particular the al-Qaeda-affiliated Jabhat al-Nusra. Once a group has seen its fortunes fall, it is hard to resuscitate it. Take, for example, Shuhada Suria (Martyrs of Syria). Just a year ago this group, which operates in the north-west province of Idleb and whose leader sits on the Supreme Military Command, was a leading fighting force. But it has faltered in part because funding has shrivelled, prompting defections to stronger groups, usually more Islamist ones. One rebel commander moans that the stinginess of foreign supplies of arms has been like “giving us injections just often enough to stop us from being killed off.”

America must stomach some arms falling into the wrong hands, too. Gulf-purchased Croatian weapons delivered to the rebels earlier this year led to gains in the south, which were reversed when supplies abruptly stopped, apparently after some were spotted in the hands of unsavoury groups including the Yarmouk Martyrs, an Islamist lot that abducted four UN peacekeepers in May. Private donations from such places as Kuwait, usually to Salafist groups, continue to bolster the sort of militias that give the rebels—in Western eyes—a bad name. A policy that fuels but does not change the dynamics of the war is “the worst of all worlds”, says Emile Hokayem, an analyst based in Bahrain for a London-based think-tank, the International Institute for Strategic Studies.

Rebel commanders hope that America’s shift includes a green light for Saudi Arabia to provide them with man-portable air-defence systems (MANPADs)—hitherto vetoed by America. That may be a forlorn hope. Mr Obama noted this month that some of the most effective opposition fighters are no friends of America, so that arming them “willy-nilly” is hardly in America’s long-term interests.

Calls to impose no-fly zones over Syria prompt similar caution in Washington. Unlike the case in Libya, where rebels held tracts of territory that could be declared off-limits to Qaddafi’s air force, the fighting in Syria often involves opposition and government forces fighting block-by-block in cities crammed with civilians. Setting up humanitarian corridors raises equally thorny questions, Mr Obama told PBS. Would America be obliged to stop not just attacks by aircraft but also missile strikes, he asked? Would that mean bombing launch sites in Damascus? What if there are civilian casualties, or an American bomb falls on a chemical weapons facility, dispersing deadly poisons?

Despite such caution, press reports suggest that American military commanders have proposed creating something akin to a no-fly zone over a sliver of Jordanian territory abutting Syria, shielding rebel training sites from cross-border attacks with the help of American F-16 fighters and Patriot missile batteries that were this month left in place in Jordan after joint military exercises. Such reports prompted a pre-emptive warning from Russia’s foreign ministry that such a no-fly zone would not “in principle” be tolerated. An American official calls such reports inaccurate, saying: “the assets in Jordan are not part of any no-fly zone efforts. Period.” But plainly the idea is under intense discussion.

Russia’s president, Vladimir Putin, did not hide sharp differences over Syria when he met Mr Obama and other leaders at a summit of the G8 countries in Northern Ireland on June 17th-18th. He said there was no proof that Syria had used chemical weapons and compared rebels to Islamist extremists accused of killing a British soldier on a London street in May. And he blocked a proposal that Mr Assad’s exit should be a precondition for convening a Geneva peace conference—a stance John Kerry, America’s secretary of state, seemed anyway to have dropped earlier.

Russia’s support for Mr Assad, involving both diplomatic cover and a steady flow of arms, is a source of intense American frustration, with Mr Obama’s team urging Russian counterparts to see that their actions are bringing about the outcome they profess to fear: a chaotic unravelling of Syria, in which religious extremists grow daily in power. Russia is keen to thwart America and sell arms, but would drop Mr Assad “in a minute” if its interests changed, Washington sources suggest.

As things stand, Mr Assad has little incentive to take the heralded Geneva conference seriously, or even attend it, while the rebels are in political and military disarray and the pressure on his regime has eased, albeit slightly. An increase in the flow of small arms to the rebels is unlikely to tilt the military balance in the short run. But Mr Assad is far from safe. The Syrian currency lost a quarter of its value on June 17th. Two days before, six of his generals and 22 colonels were said to have defected.

For all his caution, Mr Obama is being drawn closer to the conflict. Syrians keen to deepen American involvement are banking on the same mission creep that wary members of Mr Obama’s administration want to avoid. Louay Sakka of the Syrian Support Group, a Washington-based lobby, says: “Obama is now directly involved, so he has more of a stake in whether we win or lose.”