WASHINGTON -- The launch of a highly anticipated strike on Syria could make for awkward timing.

Few doubt that U.S. President Barack Obama is preparing for a U.S.-led military action to retaliate for what America and its allies say was a deadly chemical weapons attack by the Syrian government. But there are few good options for when to attack.

On Wednesday, for example, Obama will pay tribute to Martin Luther King Jr. on the 50th anniversary of the nonviolent civil rights leader's "I Have a Dream" speech.

Thursday is also problematic. That's when British Prime Minister David Cameron is set to convene an emergency meeting of Parliament, where lawmakers are expected to vote on a motion clearing the way for Britain to respond to the alleged chemical weapons attack.

On Tuesday, Obama embarks on an overseas trip that will take him away from the White House for most of the week.

Would Obama really want to be running a military operation from Sweden? Or Russia, which vigorously opposes action against Syria?

Compounding the pressure, some lawmakers and allies are urging Obama to proceed slowly and seek UN Security Council approval, while others are urging the president to act quickly and decisively. Obama's response earlier this year after the U.S. first concluded that Syrian President Bashar Assad had used chemical weapons was criticized as too little, too late.

"The longer you wait, the less meaningful it becomes," said Barry Pavel, a former top national security official in the Bush and Obama administrations.

Lawmakers from both political parties have called on Obama to consult Congress before taking action -- a step the White House says is under way. Obama also is seeking support from Western allies such as Britain and France, and from regional organizations like the 22-member Arab League, which has signalled its interest in justice for victims of the alleged chemical weapons attacks and blamed the Syrian regime.

Although Defence Secretary Chuck Hagel says the U.S. military is in position to strike as soon as Obama gives the order, the administration has yet to release a promised intelligence report formally linking Assad to the attack.

The report could be released as early as Wednesday.

A successful vote Thursday in Britain's Parliament would mark the start of short window that national security experts say could be the least worst time for Obama to act. A senior administration official said once Obama decides on what action to take, he won't delay the decision because of outside factors or competing events.

Obama on Tuesday will travel to Stockholm for his first visit as president to Sweden. The Northern European nation has claimed a position of neutrality in international conflicts for about 200 years.

Two days later, he heads to St. Petersburg, Russia, for the Group of 20 economic summit with leading foreign counterparts.

Russia, the host of the summit, is backing Assad and would be among the most vocal opponents of a military strike in Syria. A U.S.-led attack on Assad's forces while world leaders meet in Russia would be a major embarrassment for the Kremlin. It would be yet another blow to tense relations between Russia and the U.S., already at a low point since the recent U.S. decision to cancel a bilateral meeting between Obama and Russian President Vladimir Putin.

Obama's foreign travel next week will not be a factor in his decision about when to act, said the administration official, who wasn't authorized to discuss internal deliberations publicly and requested anonymity.

There's precedent for Obama to take military action while outside the U.S. It was in Brazil in 2011 when Obama, on a five-day Latin America swing, authorized limited military action against Libya to counter Moammar Gadhafi's assault on his own people.

Obama pledged last year that a chemical weapons attack would cross a red line for the U.S. Activists say hundreds were killed in the Damascus suburbs on Aug. 21.

The U.S. may also seek to wait until after the UN team in Syria investigating chemical weapons allegations has left the country. The team is scheduled to leave Syria in about a week, but the team's two-week trip could be extended.

Associated Press writer Josh Lederman contributed