WASHINGTON— President Barack Obama's next move on Afghanistan is growing more difficult by the day. Deadly attacks this week deepened British and U.N. alarm over their commitments, and fresh worries about Iraq could delay the exit of U.S. troops there, squeezing an already overstretched military.

The White House says Obama's answer on whether to expand the U.S. fighting force in Afghanistan by as much as 60 percent will be announced "in the coming weeks," the same vague timetable it has offered for much of the fall.

Obama has brushed off criticism that he is taking too long to decide whether to meet his war commander's request to provide about 40,000 more troops at the end of this year, atop a record 68,000.

But the longer the decision hangs fire, the more complications mount. The latest violence against foreign civilians and soldiers was unprecedented in scope. And that was on top of Afghanistan's perilous politics, an ongoing headache for the White House.

Obama is "taking into account the political situation, the security situation, the health of our force and all that needs to be done" to make good on the promise of dismantling the al-Qaida terror network, White House press secretary Robert Gibbs said Thursday.

The deliberations are taking place under an assumption that the Army and Marine Corps will have greater flexibility as U.S. forces are drawn down in Iraq. The withdrawal plan is hinged to Iraqi elections that are scheduled for January but now are in question.

In an e-mail this week to top Pentagon officials, the U.S. commander in Iraq, Army Gen. Ray Odierno, warned that the elections could be delayed _ potentially delaying the exit of U.S. troops with each passing day.

Odierno in September told Congress that he would keep the number of troops in Iraq _ currently about 117,000 _ steady until about two months after the election to safeguard against any surge in attacks or violence following the vote.

Barring a significant increase in violence, U.S. commanders have said about two-thirds of the troops will begin heading home almost immediately after that two-month period, bringing the number of American forces in Iraq to between 35,000 and 50,000 by the end of August 2010.

Iraqi lawmakers ended their session Thursday without agreeing to terms for the vote. They plan to try again on Saturday.