Tom Vanden Brook

USA TODAY

BRUSSELS — The war in Afghanistan — America’s longest conflict — will grind on for at least another four years as NATO allies are prepared to commit $5 billion through 2020 to train, equip and pay Afghan security forces, according to a senior NATO diplomat.

Last week, President Obama granted U.S. troops in Afghanistan expanded authority to attack Taliban insurgents. The new rules allow U.S. forces to advise regular Afghan combat units and to call in airstrikes. There are about 9,800 U.S. troops in Afghanistan, and Obama has pledged to reduce their number to 5,500 by year’s end.

Defense Secretary Ash Carter said the new, more aggressive approach put U.S. forces closer to the fight with the Taliban. The previous rules allowed, for example, for U.S. troops in Afghanistan to protect themselves and to aid Afghan forces in peril.

"We will more proactively support Afghan conventional forces in two critical ways: one, with more American firepower, especially through close air support; and two, by accompanying and advising Afghan conventional forces on the ground and in the air. In practical terms, this means that U.S. forces will have more opportunities to accompany and enable Afghan conventional forces — just like we have already been doing with Afghan special operations forces," Carter said.

The new expanded authorities will give U.S. commanders in Afghanistan more flexibility, by allowing them to identify and get pre-approval for air targets in advance, instead of just responding to emergencies, Gen. Mark Welsh, the Air Force chief of staff, told reporters in Washington.

"It will allow them to have aircraft planned to respond in support of a particular operation," Welsh said.

The Pentagon has said the new authorities will be limited to operations and missions that would have a significant impact on the battle and would not be used on a routine basis. Welsh said there are enough resources in Afghanistan now to support the expanded authority.

NATO will continue to deploy troops throughout Afghanistan into 2017, NATO secretary-general Jens Stoltenberg said Wednesday.

"We are now working on the final decisions for our exact force numbers into 2017," Stoltenberg said.

The security situation in Afghanistan remains “tough,” said the senior diplomat who spoke on condition of anonymity because officials were not authorized to speak publicly. Afghan troops still struggle to find competent leaders and supply troops in the field. Taliban insurgents continue to find safe haven in Pakistan and have exploited divisions in the Afghan government, the official said.

The official spoke to a small group of reporters at the meeting of NATO defense ministers here.

As a result of the Taliban’s resilience, NATO will continue its long-standing program to train Afghan forces, fund its military and continue to operate at air and training bases throughout the country beyond 2016, the diplomat said. Bases in the restive south at Kandahar and east in Jalalabad will remain open, the official said.

The request for authority to strike the Taliban more aggressively came from the new top commander in Afghanistan, Army Gen. John Nicholson. His assessment of security in Afghanistan and the forces he needs is expected to be announced soon.

It would not be a surprise if Nicholson asks to delay the drawdown of U.S. troops, the diplomat said. But even if the number of U.S. troops involved in training declines from 6,800 to 3,400 as scheduled, the major bases will remain open, the diplomat said. Thousands more troops are involved in counter-terrorism missions there.

Obama had planned on reducing troop levels to near zero in Afghanistan by the end of his administration. But continuing violence there has prevented that, keeping U.S. troops in combat that began in 2001.

Meanwhile, NATO defense ministers are prepared to send more trainers and aircraft to support the U.S.-led coalition fighting the Islamic State in Iraq and Syria, the official said.

Iraqi Prime Minister Haider al-Abadi has asked NATO to provide training inside Iraq, Stoltenberg said. Abadi has requested that NATO send personnel to Iraq to help its armed forces develop expertise in organizing its logistics, medical and counter-IED specialties, the diplomat said.

NATO is also prepared to offer use of its Airborne Warning and Control System (AWACS) aircraft to support the warplanes attacking ISIL targets in Iraq and Syria, Stoltenberg said.

Contributing: Jim Michaels