Trump Taliban

The strike came just hours after US special representative Zalmay Khalilzad (left) and senior Taliban officials spoke by phone with U.S. President Donald Trump on March 4
The United States has conducted a "defensive" air strike against Taliban fighters in Afghanistan's southern Helmand Province after a checkpoint manned by Afghan forces was attacked.

"The US conducted an airstrike on March 4 against Taliban fighters in Nahr-e Saraj, Helmand, who were actively attacking an #ANDSF checkpoint. This was a defensive strike to disrupt the attack," U.S. Forces-Afghanistan spokesman Sonny Leggett said in a tweet.

The strike came just hours after Taliban militants killed at least 20 Afghan security officers in a string of attacks and on the heels of U.S. President Donald Trump's "very good" chat with the Taliban's political chief.

The wave of violence is threatening to unravel a February 29 agreement signed in Doha between the United States and the Taliban that would allow allied forces to leave Afghanistan within 14 months in return for various security commitments from the extremist group and a pledge to hold talks with the Afghan government -- which the Taliban has so far refused to do.

Afghan President Ashraf Ghani has warned he was not committed to a key clause in the deal involving the release of up to 5,000 Taliban prisoners.

The Taliban said it would not take part in intra-Afghan talks until that provision was met.

And on March 2, the militant group ordered its fighters to resume operations against Afghan forces, saying that a weeklong partial truce between the Taliban, U.S., and Afghan forces that preceded the Doha agreement was "over."

"Taliban fighters attacked at least three army outposts in the Imam Sahib district of Kunduz last night, killing at least 10 soldiers and four police," said Safiullah Amiri, a member of the provincial council.

Another attack killed six soldiers in the same northern region, Amiri added.

Washington has said it would defend Afghan forces if they came under Taliban attack.