Military leaders have increasingly suggested that Obama’s political promises are restricting their ability to fight. On Wednesday, former defense secretary Robert M. Gates, still an influential figure at the Pentagon, bluntly criticized his former boss.

“There will be boots on the ground if there’s to be any hope of success in the strategy,” Gates said in an interview with CBS News, adding that “the president in effect traps himself” by repeating his mantra that he won’t send U.S. troops into combat.

There are signs that the White House is becoming more flexible. Antony Blinken, the deputy national security adviser, allowed Thursday that “there may be cases where American advisers would go with some of the forces on the ground” or help “to call in some air power” — the kind of leeway the Pentagon wants.

In an interview with MSNBC, Blinken insisted that such deployments would not amount to combat “where Americans are on the ground leading the fight. That is not going to happen. That’s not part of this campaign. The president’s been clear about that.”