Al Qaeda in Afghanistan could regenerate and plot terrorist attacks against the American homeland within two years, possibly sooner if the insurgent Taliban overwhelm a fragile U.S.-backed government and take control of the country, top Pentagon officials warned Thursday.

With mounting evidence that the Taliban have maintained close ties with al Qaeda, a collapse of the Afghan government and subsequent Taliban takeover could produce a country that is ground zero for global Islamic terrorism — just as it was in the years leading up to the Sept.

I would also say … it would take possibly two years for them to develop that capability” to carry out terrorist attacks outside Afghanistan, Mr.

“If certain other things happen, if there was a collapse of the government or the dissolution of the Afghan security forces, that risk would obviously increase,” he said.

Pockets of insurgents and largely independent terrorist cells can wreak havoc locally in the form of mass shootings or suicide bombings, but having physical territory to train and plan takes the threat to an entirely new level, said Nathan Sales, a State Department counterterrorism coordinator in the Trump administration.

“When terrorist groups control territory, that enables them to plot attacks against the homeland, against Europe, against our allies in the region and around the world,” he said.

Because ISIS had a so-called caliphate in Iraq and Syria, we got [terrorist attacks in] Paris and Brussels in 2015 and 2016.”.

Military leaders said they will use “over the horizon” counterterrorism capabilities such as drone strikes to hit al Qaeda, ISIS and other groups in Afghanistan before they can grow into major fighting forces.

A collapse of the Afghan government and ascension of the Taliban would represent a historic foreign policy disaster for the U.S., which invaded the country nearly 20 years ago to topple the Taliban government after the 9/11 attacks and has been battling the group ever since.

Among other things, the Taliban promised a permanent break with groups such as al Qaeda and said Afghanistan would never again become a sanctuary for terrorist organizations.

But a United Nations assessment released on June 1 found that al Qaeda maintains a major presence in Afghanistan and is deeply intertwined with the Taliban

“Large numbers of al Qaeda fighters and other foreign extremist elements aligned with the Taliban are located in various parts of Afghanistan

Al Qaeda continued to suffer attrition during the period under review, with a number of senior figures killed, often alongside Taliban associates while co-located with them,” the study said

“Ties between the two groups remain close, based on ideological alignment, relationships forged through common struggle and intermarriage,” said the report, produced by the U.N

Against that backdrop, specialists say, it’s unclear whether the Taliban and al Qaeda are brazen enough to rebuild their pre-9/11 infrastructure and plan attacks against the U.S