The US’s top military general has warned that the collapse of the Afghan government and return of Taliban rule could accelerate the possible threat of terrorist groups reforming in the country.

The chairman of the joint chiefs of staff, Mark Milley, issued his warning to congressional leaders during a Sunday morning phone briefing on the Afghan crisis between top officials from the Biden administration and a bipartisan group of members of Congress, Axios reported

The nation’s highest-ranking military officer is reported to have said that previous assessments that terrorist groups could rise up again in the country within two years are likely to be revised, with the timeline brought forward.

Milley was reportedly asked by Republican senator Lindsey Graham whether the resurgence of the Taliban would lead to a revision of the risk assessment. “Yes,” he replied, adding that he assumed the two-year timeline would be shortened.

The current risk assessment was revealed in June when Lloyd Austin, the defense secretary, told senators that he put the likelihood of terrorist groups finding their way back to Afghanistan at “medium”. “I would assess it as medium, it would take possibly two years for them to develop that capability,” he said then.

The question of whether the dramatic return to power of the Taliban could lead to Afghanistan once again being used as a launch-pad for terrorist groups targeting the US is the most politically-charged element of the current crisis for Washington. It was the presence of al-Qaida camps in Afghanistan at the time of the 9/11 terror attacks that sparked the US war almost 20 years ago.

The Biden administration has tried to justify the chaotic withdrawal from Afghanistan by saying its mission of ousting al-Qaida from the country had been completed years ago. Osama bin Laden, the al-Qaida leader, was killed by US special forces in Pakistan more than a decade ago.

Any evidence that terrorist organisations were making a comeback under renewed Taliban rule could be politically toxic for the Biden administration. The US secretary of state Antony Blinken told CNN’s State of the Union on Sunday that over the past two decades modern methods had been developed for containing terrorist organisations that did not rely on a military presence on the ground in Afghanistan.

“We have tremendously more capacity now than we had before 9/11. We are going to retain in the region the over-the-horizon capacity to see and deal with any reemergence of a terrorist threat,” Blinken said.

The Pentagon has said it has been developing such “over-the-horizon” logistics – meaning the capability to monitor and strike Afghan locations using fighter jets and drones based in other countries – over the past several months. But the task of keeping any reforming terrorist groups in check from a distance is no easy challenge.

Currently the US has no military bases in any of the six countries that border Afghanistan. The nearest bases are in the Gulf, several hours of flight-time away, which in turn reduces the operational abilities of the aircraft.