US President Donald Trump on Monday travelled to Dover Air Force Base in Delaware to pay tribute to two soldiers who were killed on Saturday in Afghanistan when a soldier dressed in an Afghan army uniform opened fire with a machine gun.

According to the National security adviser, Robert O’Brien told to media travelling with Trump on Air Force One that the president wrapped up a reelection campaign rally in New Hampshire a bit early so he could visit with the families of the soldiers.

O’Brien also described such moments as probably the toughest thing he does as president, along with visiting wounded soldiers at Walter Reed National Military Medical Center.

These are terrible sacrifices for the families. And these guys are heroes, they’re real warriors and did a great job for the American people,” O’Brien added.

The Defense Department has identified the dead American soldiers as Sgt. Javier Jaguar Gutierrez, 28; and Sgt. Antonio Rey Rodriguez, 28. Six other American soldiers were wounded in the attack.

The US and Afghan forces came under attack in eastern Afghanistan as they launched investigations into what the New York Times described as a deadly shootout between Afghan and American soldiers during a joint exercise.

Washington’s peace envoy Zalmay Khalilzad has been meeting with Taliban representatives in the Middle Eastern state of Qatar in recent weeks.

He’s seeking an agreement to reduce hostilities to get a peace deal signed that would start negotiations among Afghans on both sides of the conflict.

On Tuesday, in his State of the Union Address, Trump referenced the peace talks, saying US soldiers were not meant to serve as law enforcement agencies for other nations.

Sohrab Qaderi, a provincial council member in Nangarhar, said clashes happened between the Afghan army and foreign forces in Shirzad district on Saturday afternoon.

Some 13,000 US troops remain in Afghanistan after the US intervention to oust the Taliban following the 11 September 2001 attacks.

The Taliban now control more territory than at any point since they were ousted in 2001, the BBC reported.

Peace talks between the US and the militants have stalled in recent months.

(With inputs from agency)