BETHESDA, Maryland (REUTERS) - President Donald Trump visited wounded US service members at Walter Reed National Military Medical Centre on Saturday (April 22), his first visit as president to the armed forces hospital in Bethesda, Maryland, outside Washington.

Accompanied by his wife, Melania, Trump awarded Army Sergeant First Class Alvaro Barrientos the Purple Heart, the medal given to members of the US military wounded or killed in battle.

Barrientos was injured in Afghanistan on March 17 when an Afghan soldier opened fire inside a base in Helmand province, wounding three US soldiers. Barrientos' right leg was amputated, according to a White House official.

The President put his hand on the sergeant's shoulder and kissed the sergeant's wife, Tammy, on the cheek. Then he pinned the Purple Heart to the sergeant's lapel and clapped him on the back.

"When I heard about this, I wanted to do it myself... Congratulations, tremendous," Trump told Barrientos.

During his eight years as president, Barack Obama made visits to Walter Reed a regular occurrence, particularly when the wars in Iraq and Afghanistan were raging. He ended up visiting the hospital more than 20 times.

While this was Trump's first visit there, he did make a trip to Dover Air Force Base in Delaware in February to honour a service member killed during an operation in Yemen.

Trump is spending the weekend in rainy Washington. He has recently been criticised for his frequent trips to his Florida resort, Mar-A-Lago, which Democrats say are costing taxpayers millions of dollars for travel and security.

Leaving the White House, Trump's motorcade passed dozens of protesters gathered along its route holding signs for a March for Science being held in downtown Washington, one of series of such Earth Day events being held across the country.