WASHINGTON — President Bush's top defense advisers have recommended he maintain 15 combat brigades in Iraq until the end of the year, contrary to expectations that the improved security in Iraq would allow for quicker cuts, The Associated Press has learned.

Military leaders told the AP that the closely held plan would send a small Marine contingent to Afghanistan in November to replace one of two Marine units expected to head home then.

If Bush follows the recommendations, he would delay any additional buildup in Afghanistan until early next year, when another brigade would be deployed there instead of to Iraq.

That move would cut the number of brigades in Iraq to 14 in February.

The plan is aimed at taking advantage of security gains in Iraq to bolster troops in Afghanistan, where violence is on the rise. Several senior military and defense officials described the recommendations on condition of anonymity since the plan has not been made public.

They also acknowledged the plan is a compromise, since Gen. David Petraeus, the top U.S. commander in Iraq, argued to maintain the current force levels in Iraq — about 146,000 troops including 15 combat brigades and thousands of support forces — through June.

Bush is weighing the plan; in the past, he has largely accepted the military's advice.