WASHINGTON (Reuters) - U.S. President Barack Obama may not decide before a NATO summit next month whether to alter plans to nearly halve America’s forces in Afghanistan, a diplomat and a U.S. official said.

U.S. Army soldiers of 2nd Battalion, 1st Infantry Regiment take up positions while Afghan soldiers search motorists, during a joint U.S.-Afghan military patrol in a village in Arghandab Valley in Kandahar province, southern Afghanistan October 22, 2012. REUTERS/Erik De Castro

A decision had been expected at or before the summit in Warsaw on July 8-9 on whether to stick to plans to slash the 9,800 troops to 5,500 before Obama leaves office next year.

Former commanders and envoys have warned that it would be a mistake. And with preparations in full swing for the summit, the timing of any decision by Obama remains unclear.

U.S. Defense Secretary Ash Carter flies to Brussels on Monday to meet NATO counterparts, with Afghanistan expected to be high on the agenda.

One reason to decide on slowing the U.S. drawdown before the summit might be to encourage NATO allies to keep their troops in Afghanistan, where President Ashraf Ghani’s government is battling a Taliban insurgency that has gathered fresh momentum.

NATO allies seem less intent on cutting their troop presence, which could give Obama more time to formulate and telegraph his own plans.

“We have been moderately, pleasantly surprised at the willingness to stay at current levels of most other allies, and

some willingness to consider increasing,” said the diplomat, who

spoke on condition of anonymity.

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“Just because there is a summit doesn’t mean (you) need a decision,” he added.

To be sure, Afghanistan will be a major issue at the summit and Obama still could make a decision before then.

“It does not have to happen by Warsaw but it certainly will be a topic there,” said a U.S. official who spoke on condition of anonymity. “The size and scope of other nation contributions are a logical consideration in our decision-making.”

The White House has yet to receive the recommendations from its new commander in Afghanistan, General John Nicholson, who conducted a comprehensive security review during his first 90 days on the job. The review’s results have not been made public.

In a sign of his willingness to broaden the U.S. role in Afghanistan, Obama last week approved giving the U.S. military greater ability to accompany and to enable Afghan forces in offensive operations, including carrying out air strikes.

Speaking on Friday, White House spokesman Josh Earnest told reporters the decision to broaden the remit “does not limit in any way our ability to follow through with the plan to draw down our troops at a level of 5,500 troops by the end of this year.”

Obama would consider changing the troop numbers if Nicholson recommended that, Earnest said.

Speaking to reporters as he flew to Brussels on Monday, Carter declined to speculate on when Obama might make such a decision, but stressed that the president has been open to considering recommendations from the military.

“I don’t know the answer to your question, ‘When?’, and I don’t think the President’s made a decision in that regard,” Carter said during his flight to Brussels, when asked if a decision might come by the Warsaw summit.

Nicholson’s predecessors and former U.S. envoys to Afghanistan urged Obama earlier this month to keep troop levels steady at near 10,000 through the remainder of his term.

"This approach would also allow your successor to assess the situation for herself or himself and make further adjustments accordingly," the letter read. It can be viewed here: bit.ly/1RT87FS

Cutting the forces to 5,500, in turn, would erode the morale of Afghan government forces and bolster the Taliban, they wrote.

Obama has already scaled back the troop withdrawal plans he laid out in May 2014, when he pledged to cut to roughly 5,000 by end 2015 and to “a normal embassy presence ... with a security assistance component, just as we’ve done in Iraq” by the end of 2016.

Among the factors weighing in his troop decision include how much, if any, additional support he may get from other NATO nations; the signal that a cut will send to Ghani and to the Taliban; and what kind of legacy he leaves his successor.