Prospects for an agreement that could lead to withdrawal of all American troops from Afghanistan are “very promising,” U.S. Secretary of Defense Mark Esper said on Saturday.

U.S. emissaries have been talking with leaders of the Taliban organization, which once ruled Afghanistan, for months. Afghan government officials have played only a peripheral role.

The brutally Muslim extremist Taliban ruled Afghanistan for many years before being ousted by a U.S.-led invasion in the wake of the Sept. 11, 2001 attacks on America by al-Qaida terrorists. That military action came only after the Taliban, who had provided a safe haven for al-Qaida, refused to give up the terrorists, it should be noted.

But during the nearly 20 years since they were booted out of power, the Taliban have been keeping up the fight to regain it. They have been gaining control over larger and larger swaths of Afghanistan.

Americans have grown sick of the cost in both blood and money of our continued presence in Afghanistan. One of President Donald Trump’s campaign pledges in 2016 was to withdraw U.S. troops from the country.

To Trump’s credit, that pledge was conditional on a Taliban agreement to reduce the scale of attacks on Americans. On at least a couple of occasions, Trump has drawn back from talks when it became clear the Taliban were not holding up their end of that bargain.

Now, however, it appears some sort of breakthrough may be in the offing. On Saturday, Esper said, “we have on the table right now a reduction in violence proposal that was negotiated between our ambassador and the Taliban. … the best, if not the only, way forward in Afghanistan is through a political agreement, and that means taking some risk.”

Not really. The only risk is that if U.S. officials agree to a withdrawal arrangement, the Taliban will continue attacks on our troops.

If that happens, Trump should respond with stepped-up assaults on the Taliban.

But there really is no question about what will happen if U.S. troops are pulled out of Afghanistan. The Taliban will regain control over that country.

For that reason, Trump should make one thing crystal clear:

If the Taliban does regain control, they must not resume hosting terrorist groups such as al-Qaida.

If that happens, the Taliban should be assured, the full might of U.S. military power will come down on them again.