WASHINGTON >> The pace of U.S. troop withdrawals from Afghanistan will headline Afghan President Ashraf Ghani’s visit to Washington, yet America’s exit from the war remains tightly hinged to the abilities of the Afghan forces that face a tough fight against insurgents this spring.

President Barack Obama has promised to end the longest U.S. war — it began in the aftermath of the Sept. 11, 2001, terror attacks — and get the remaining troops out of Afghanistan by the end of his presidency. Deficiencies in the Afghan security forces, heavy casualties in the ranks of the army and police, a fragile new government and fears that Islamic State fighters could gain a foothold in Afghanistan have combined to persuade Obama to slow the withdrawal.

Instead of trimming the current U.S. force of 9,800 to 5,500 by the end of the year, U.S. military officials say the administration now might keep many of them there well into 2016. Obama had said that after that, the U.S. would only maintain an embassy-based security force in Kabul of perhaps 1,000 troops. But on Friday, Jeff Eggers of the White House’s National Security Council said that too could be changed. He said the post-2016 plan will be considered on an on-going basis.

At stake is the U.S. taxpayers’ more than $60 billion investment — so far — in the Afghan forces. The 327,000-member force performs much better than before, but still needs work.

While praising their ability to operate mostly independently and securing the nation during a protracted election, U.S. military officials say the Afghan forces still suffer from a host of problems: attrition, drug abuse, desertions, illiteracy, poor record-keeping, a lack of management and logistical skills, intelligence, a shortage of top-notch leaders and less-than-optimal cooperation between policemen and soldiers.

They also are suffering massive casualties as they ramp up operations.

More than 1,300 members of the Afghan army were killed in action and another 6,200 were wounded in action between October 2013 and September 2014, according to a report this month from the special inspector general for Afghan reconstruction. Casualties in the ranks of policemen are even higher. In nearly 14 years of fighting, at least 2,200 U.S. military service men and women have been killed.

“They are now leading the fight, but they still need our support, and that support is critical to enabling them to hold the key cities … and to hold off a still bubbling insurgency, particularly in the rural areas,” Michele Flournoy, former undersecretary of defense for policy, said last week at an event organized by the Alliance in Support of the Afghan People.

Afghan leaders also worry that Islamic State militants could push into the region and bring guns and money that would spark competition among insurgents disenchanted with the Taliban leadership and eager to prove their prowess with heinous acts of violence. Afghan and U.S. officials say some Afghan militants have rebranded themselves with IS, raising its black flag and even clashing with Taliban fighters.

Army Gen. John Campbell, the top U.S. commander in Afghanistan, told a congressional panel recently that the Afghans repeatedly ask the U.S. for close air support, which has been critical in their ability to fend off Taliban fighters battling to capture territory.

“What I tell the Afghans is, ‘Don’t plan your operation wholly dependent upon close air support. The Taliban doesn’t have close air support. The Taliban doesn’t have up-armored Humvees. The Taliban doesn’t have D-30 Howitzers. The Taliban doesn’t have, you know, the weapons that you have,'” Campbell said.

The Afghan Air Force, which currently has about 100 aircraft, is slated to receive 20 light-attack aircraft used for counterinsurgency, close air support and aerial reconnaissance, but more than half aren’t slated to arrive until 2017 and 2018.

“That’s another reason we need to continue to have this train, advise and assist (mission) for the next several years,” Campbell said.

Nearly 14 years after the U.S. invaded after 9/11 to root out al-Qaida and oust its host, the Taliban, Afghanistan remains a dangerous country.

The United Nations reports that 3,700 Afghan civilians were killed and another 6,850 were injured in the conflict last year, more than any year since it started documenting civilian casualties.

Going forward, lawmakers must weigh the risks that come with cutting the purse strings amid reports of wasteful spending, fraud and corruption. Rep. Walter Jones, R-N.C., suggested at a House committee hearing that the U.S. might want to “stop pounding money down the rat hole.”

“When that rat hole is Afghanistan,” he said, “the billions are essentially without end.”

So far, Congress has appropriated more than $60 billion to build, equip, train, and sustain the Afghan forces, and the Defense Department has asked for an additional $3.8 billion for fiscal 2016.

Robert Hathaway, former director of the Asia program at the Woodrow Wilson Center, said financing Afghanistan is likely to become a contest of endurance between the Taliban, and the U.S. taxpayer and members of Congress.

“I think inevitably — both because of fiscal pressures and because of the nature of the warfare in Afghanistan — we are going to see, a few years down the road, a smaller, leaner sleeker Afghan army,” Hathaway said. “Whether or not it will be a more effective army, I think, remains to be seen, but it’s going to be a very, very tough slog ahead.”