WASHINGTON — President Trump, due to unveil his new strategy for fighting the war in Afghanistan, faces what some aides are calling a “victory problem” — how to define success in America’s longest war and sell the war-weary U.S. public on the possibility of sending a few thousand more troops into the nearly 16-year-old conflict.

In recent days, White House officials have declined to say whether the new approach will roll out by mid-July — in keeping with a timetable Defense Secretary Jim Mattis laid out weeks ago. And they won’t say what role the commander in chief might play in selling the plan, including a potentially open-ended commitment, to Americans.

“We have a ‘victory problem,’” a senior administration official recently told Yahoo News, speaking on condition of anonymity to describe internal debates.

“Not everyone agrees on how to define it, and definitely not everyone agrees on how to pursue it. We don’t completely agree on ends, and we definitely don’t completely agree on means. And we won’t, even after a strategy rolls out.”

The question of how to define victory in Afghanistan bedeviled both of Trump’s predecessors. And now, a decade and a half after the first U.S. bombs fell there, it falls to the former real estate developer with a penchant for short declarations on even the most complex issues.

“Now, we never win a war. We never win. And we don’t fight to win. We don’t fight to win,” Trump complained to the National Governors Association in late February. “So we either got to win or don’t fight it at all.”

Since George W. Bush unleashed U.S. military might against the Taliban on Oct. 7, 2001, some 2,400 Americans have died in the conflict and more than 20,000 have been wounded. Barack Obama surged tens of thousands of troops into Afghanistan in 2009 but later drew frequent criticisms from Republicans, who accused him of focusing on withdrawing U.S. forces rather than defeating the Taliban. Obama aides said their main goal was making local security forces self-sustaining in order to extricate the United States from a seemingly intractable conflict.

Inside the Trump administration and among outside experts, there’s a general consensus that America’s foremost national security goal is to prevent Afghanistan from slipping back into its pre-9/11 state as a safe haven for extremists plotting to strike at America or its allies.

After that, though, things get murky. How many U.S. troops are needed? How many will stay for how long? How many are NATO allies willing to send, and to play what role? How much responsibility does America bear to build or shore up Afghan institutions, a process that candidate Trump (and his most fervent supporters) would likely have rejected as wasteful “nation-building”?

“Success is defeating the ISIS and al-Qaida in Afghanistan, and secondly an Afghan government that does not melt down, does not collapse, and is able to control its territory enough so that it does not become a safe haven for terrorists who threaten the U.S. and its allies,” Stephen Hadley, who served as George W. Bush’s national security adviser, told Yahoo News.

“We want the Afghan people to build a healthy, prosperous democracy — it is key to long-term peace and prosperity in Afghanistan, and we should certainly support that effort,” Hadley said. “But that’s primarily their job, their responsibility and will take a long time.”

Leon Panetta, who served as defense secretary and CIA director under Obama, said the United States must help the Afghan government and security forces.