Top Pentagon officials on Thursday said that militant groups like al Qaeda could pose a threat from Afghanistan to the United States and American allies in two years after the full withdrawal of international troops from the country.

US President Joe Biden’s decision to withdraw all troops from Afghanistan in the next few months has been accompanied by concerns about Afghanistan’s future, especially when it comes to containing threats from terrorist groups in the country.

“It would take possibly two years for them to develop that capability,” US Defense Secretary Lloyd Austin said during a congressional hearing on Thursday.

Meanwhile, Gen. Mark Milley, Chairman of the US Joint Chiefs of Staff, said he agreed with the timeline and said there was a medium risk at the moment.

“If there was a collapse of the government or a dissolution of the Afghan security forces, that risk would obviously increase,” Milley said.

The remarks come as a UN report in January said there are at least 500 al Qaeda fighters in Afghanistan and that the Taliban maintains a close relationship with the group. The Taliban has denied having ties with al Qaeda.

Also, US National Security Adviser Jake Sullivan meanwhile said on Thursday that they take the issue seriously that militant groups in Afghanistan will pose threat to the west.

“Obviously, we take seriously the concern that the Taliban or other elements in Afghanistan will attack the Western — or the international presence — diplomatic presence or security presence in and around Kabul. That’s why we are putting together a detailed and effective security plan,” Sullivan said.

This comes as violence has intensified following the start of the withdrawal of US and coalition forces from Afghanistan. A parliamentary committee on Thursday reported fighting on 200 fronts across the country in just a day. Moreover, at least 30 districts have fallen to the Taliban in the last two months.