President Barack Obama and his administration allies are intensifying a public-relations offensive in what even Obama has called a “heavy lift” to win public and congressional support for a military strike on Syria.

The White House effort includes appearances by Mr Obama’s chief of staff, Denis McDonough, on all five of the US network talk shows broadcast today.

Mr Obama will follow up with six television network interviews tomorrow before giving a prime-time televised address to the nation on Tuesday.

After failing to persuade allies at the G20 summit in Russia last week to unite behind military action, Mr Obama returned to Washington to press his request for congressional authorisation for a “limited” military strike to punish Syrian President Bashar al-Assad for what the US says was a chemical weapons attack.

The August 21st assault near Damascus killed more than 1,400 people, many of them children, according to US intelligence.

“He’s got to emphasise the importance of this issue for credibility of the United States globally,” Stephen Hadley, a national security adviser to President George W Bush, said in an interview with Bloomberg Television’s Political Capital with Al Hunt.

“It’s going to be hard, but it’s really the only option.”

Almost six in 10 Americans oppose the US conducting a unilateral missile strike against Syria, according to a Washington Post/ABC News poll.

Seventy per cent oppose supplying weapons to the Syrian rebels, according to the poll of 1,012 adults, which was taken August 28th to September 1st and has an error margin of plus or minus 3.5 percentage points.

While many members of Congress remain undecided, more have voiced opposition or doubt about Mr Obama’s authorisation request than have endorsed it.

Mr Obama’s difficulties were compounded yesterday in the Senate, which is scheduled to begin debate tomorrow and vote this week on a resolution approving force.

Democratic Senator Mark Pryor of Arkansas, who faces re- election next year in a state Mr Obama lost in his 2012 re- election, issued a statement saying he opposes US military action in Syria “at this time” because the administration hasn’t proved “a compelling national security interest” or provided a clearly defined mission for an attack.

The challenge may be even steeper in the Republican-controlled House, where Mr Obama must overcome opposition from Tea Party Republicans, anti-war Democrats and members of both parties concerned about drawing the US into another Mideast conflict.

“I knew this was going to be a heavy lift,” Mr Obama said on Friday at a press conference in St Petersburg, Russia, after the G20 meeting of economic powers. “I understand the scepticism. I think it is very important, therefore, for us to work through, systematically, making the case to every senator and every member of Congress. And that’s what we’re doing.”

YouTube Videos

As part of the campaign for support, the Senate intelligence committee posted online yesterday 13 videos that “claim to show victims of a chemical or poison gas attack,” according to the committee’s website.

The videos were posted on Google Inc’s YouTube by Syrian opposition groups, according to the committee, whose chairman, Democratic Senator Dianne Feinstein of California, backs Mr Obama’s call for a use-of-force resolution.

The videos, compiled by the Open Source Center run by the Central Intelligence Agency, show victims lying on a floor, convulsing and foaming at the mouth. They also show rows of dead bodies.

The opposition-supplied videos provide no evidence of who was responsible for the attack. A US intelligence report released last month assessed “with high confidence” that the Syrian government conducted the chemical weapons attack, although it stopped short of saying who gave the order to use the weapons and whether a rogue element of the regime could have been responsible.

Former administration officials also have been lending their voices on Mr Obama’s behalf, with former Central Intelligence Agency director David Petraeus and former defence secretary Robert Gates issuing statements urging Congress to approve a strike.

Senator John McCain, an Arizona Republican who backs military action, yesterday spotlighted the Petraeus statement on a Twitter Inc. post that said, “Gen David Petraeus strongly urges action on Syria - the most respected military leader of our time.”

Lawmakers in both parties have expressed concern that the US may be drawn into the 2 1/2 year-old Syrian civil war, in which more than 100,000 people have died, or a conflict that expands to include other regional actors, such as Iran or Hezbollah.

“Given the case that has been presented to me, I believe that a military strike against Syria at this time is the wrong course of action,” Senator Joe Manchin, a West Virginia Democrat, said in a statement last week.

“I believe that we must exhaust all diplomatic options and have a comprehensive plan for international involvement before we act.”

Mr Obama’s weekly radio and internet address yesterday provided a preview of his appeal that “what we’re talking about is not an open-ended intervention. This would not be another Iraq or Afghanistan. There would be no American boots on the ground.”

Failing to act, he said, “would increase the risk that chemical weapons could be used again, that they would fall into the hands of terrorists who might use them against us, and it would send a horrible signal to other nations that there would be no consequences for their use of these weapons.”

Bloomberg