WASHINGTON (AP) ― Warily watching to see how many U.S. troops might remain in Afghanistan next year, American diplomats and aid workers are facing a withdrawal of their own as security threats and dwindling resources limit their 12-year push to develop nation.

Nearly $100 billion has been spent since 2001 on U.S. projects to better Afghan lives after generations of war and isolation, including boosting security forces, educating young girls and launching mobile phone technology.

But the State Department’s ability to continue aid programs, or start new ones, hinges largely on Afghanistan’s security ― and whether officials can travel to project sites to make sure the money is being spent wisely. A long-delayed decision on whether as many as 10,000 American forces personnel will remain in Afghanistan after the war ends this year will determine how deeply the aid will be cut.

It’s an all-too-familiar pattern of anxiety for diplomats who saw years of development projects in Iraq wither away after U.S. troops withdrew in 2011 because of reduced resources and increased security threats.

“It was not ... particularly pleasant to have to take a very large program down to a very small program in a very short period of time,” said Assistant Secretary of State William Brownfield, who oversaw a gutting of State Department aid to Iraqi police forces two years ago. Violence in Iraq has surged ever since.

Brownfield told reporters last week that he is already anticipating fewer personnel and less money for local legal programs in Afghanistan, including fighting drug traffic and helping prosecutions and prison systems.

But he’s waiting to see how many security force personnel might remain before he can predict how deep the cuts will be.

“My intent is to have established a policy and a strategy that can adjust to these realities without having to do the savage surgery that I was required to do in Iraq in 2012,” Brownfield said.

Congress already is seeking to halve all foreign assistance to Afghanistan, he said.

U.S. lawmakers are all too aware of the tough balance between inevitable budget cuts and trying to keep a U.S. foothold in Afghanistan after more than 12 years of war.

“There’s a credibility question,” said Sen. Bob Casey (Democrat-Pennsylvania), who until last summer chaired a panel on South and Central Asia on the Senate Foreign Relations Committee. “We have plenty of reasons to make sure when the military engagement ends that we really maintain both a diplomatic presence and strategy.”

However, he said, “it’s very hard for most taxpayers to support” keeping a large military presence in Afghanistan.

Negotiations over whether foreign military forces should remain in Afghanistan after the combat mission ends in December have snarled over Afghan President Hamid Karzai’s refusal to sign a security agreement with the United States. Without such an agreement, allies have said NATO forces will not remain.

On Tuesday, U.S. military officials said the number of American troops in Afghanistan could drop to as low as 20,000 by mid-summer, giving commanders the ability to pull them all out by the end of the year if no agreement is reached. It generally takes about 10 months to shut down a massive military base, but officials said the Pentagon is prepared to do it in a much shorter -- although far more expensive -- timeline.

Officials have said that plans for a post-2014 force would put U.S. and NATO troops in four regions across Afghanistan, with American troops commanding in the south and east. They would be spread across 10 bases -- down from the current 80 or so. The officials spoke on condition of anonymity Tuesday because they were not authorized to be named while discussing the plans.

So far, the U.S. has allocated $96 billion to build up Afghanistan -- more than half of it to train and equip the nation’s estimated 344,000 security forces. Continued support for the Afghan troops, which are expected to grow by another 8,000, will be a key predictor to the country’s stability after 2014.

“While there are still American troops in the field, you get funding for the troops. If American troops aren’t there, the administration’s ability to sustain funding for the (Afghan national security forces) gets a lot more problematic,” said Stephen Biddle, a national security and defense expert at the Council on Foreign Relations.

“And if that goes away, the whole show collapses,” Biddle said. “It’s very hard to imagine road projects, wells, schools, clinics -- the kinds of things we’ve been sinking money into -- surviving in that kind of environment.”