Donald Trump has given the Pentagon complete authority to set troop levels in Afghanistan, hours after his Defence Secretary suggested the US was losing the war.

Defence Secretary James Mattis told Senate Appropriations Subcommittee on Defence that the President had delegated him complete authority over the number of troops, as he had previously done for the conflicts in Syria and Iraq.

The day before, Mr Mattis had told the Senate Armed Services Committee that the US was “not winning” the war in Afghanistan.

“The Taliban had a good year last year, and they’re trying to have a good one this year,” he said. “Right now, I believe the enemy is surging.”

Many felt the Secretary was hinting he wanted to send more troops to the country. General John Nicholson, the top US commander in Afghanistan, said earlier this year that he needs “a few thousand” more troops in the fight against Isis, the Taliban, and other militant groups.

In a statement on Wednesday, however, Mr Mattis said his newfound authority "does not in itself change the force levels for Afghanistan".

"Rather, it ensures the Department of Defence can facilitate our missions and align our commitment to the rapidly evolving security situation, giving our troops greater latitude to provide air power and other vital support," the Secretary continued.

Afghanistan: Between Hope and Fear Show all 16 1 /16 Afghanistan: Between Hope and Fear Afghanistan: Between Hope and Fear 2001 Afghans at the Killi Faizo refugee camp desperately reach for bags of rice being handed out to the thousands who escaped the bombardment in southern Afghanistan during Operation Enduring Freedom. (Chaman, Pakistan, December 4, 2001) Paula Bronstein Afghanistan: Between Hope and Fear 2002 Mahbooba stands against a bullet-ridden wall, waiting to be seen at a medical clinic. The seven-year-old girl suffers from leishmaniasis, a parasitical infection. (Kabul, March 1, 2002) All photos Paula Bronstein Afghanistan: Between Hope and Fear 2003 A mother and her two children look out from their cave dwelling. Many families who, fleeing the Taliban, took refuge inside caves adjacent to Bamiyan’s destroyed ancient Buddha statues now have nowhere else to live. (Bamiyan, November 19, 2003) Paula Bronstein Afghanistan: Between Hope and Fear 2007 Students recite prayers in a makeshift outdoor classroom in the Wakhan Corridor, a mountainous region in northeastern Afghanistan that extends to China and separates Tajikistan from India and Pakistan. (Northeastern Afghanistan, September 2, 2007) Paula Bronstein Afghanistan: Between Hope and Fear 2007 Bodybuilders in the 55-60 kg category square off during a regional bodybuilding competition. Many Afghan men, like others around the world, feel that a macho image of physical strength is important. (Kabul, August 6, 2007) Paula Bronstein Afghanistan: Between Hope and Fear 2008 A woman in a white burqa enjoys an afternoon with her family feeding the white pigeons at the Blue Mosque. (Mazar-e-Sharif, March 8, 2008) Paula Bronstein Afghanistan: Between Hope and Fear 2009 Addicts inject heroin while trying to keep warm inside the abandoned Russian Cultural Center, which the capital city’s addicts use as a common gathering point. Heroin is readily available, costing about one dollar a hit. (Kabul, February 9, 2009) Paula Bronstein Afghanistan: Between Hope and Fear 2009 An elderly man holds his granddaughter in their tent at a refugee camp after they were forced to flee their village, which US and NATO forces had bombed because, they claimed, it was a Taliban hideout. (Surobi, Nangarhar Province, February 7, 2009) Paula Bronstein Afghanistan: Between Hope and Fear 2009 Seven-year-old Attiullah, a patient at Mirwais Hospital, stands alongside an X ray showing the bullet that entered his back, nearly killing him. Attiullah was shot by US forces when he was caught in a crossfire as he was herding sheep. (Kandahar, October 13, 2009). Paula Bronstein Afghanistan: Between Hope and Fear 2010 US Army Sargeant Jay Kenney (right), with Task Force Destiny, helps wounded Afghan National Army soldiers exit a Blackhawk helicopter after they have been rescued in an air mission. (Kandahar, December 12, 2010) Paula Bronstein Afghanistan: Between Hope and Fear 2010 An Afghan National Army battalion marches back to barracks at the Kabul Military Training Center. (Kabul, October 4, 2010) Paula Bronstein Afghanistan: Between Hope and Fear 2014 Eid Muhammad, seventy, lives in a house with a view overlooking the hills of Kabul. He and millions of other Afghans occupy land and housing without possessing formal deeds to them. (Kabul, November 21, 2014) Paula Bronstein Afghanistan: Between Hope and Fear 2014 Razima holds her two-year-old son, Malik, while waiting for medical attention at the Boost Hospital emergency room. (Lashkar Gah, Helmand Province, June 23, 2014) Paula Bronstein Afghanistan: Between Hope and Fear 2014 Young women cheer as they attend a rally for the Afghan presidential candidate Ashraf Ghani. (Kabul, April 1, 2014) Paula Bronstein Afghanistan: Between Hope and Fear 2014 Burqa-clad women wait to vote after a polling station runs out of ballots. (Kabul, April 5, 2014) Paula Bronstein Afghanistan: Between Hope and Fear 2015 Relatives, friends, and women’s rights activists grieve at the home of Farkhunda Malikzada, who was killed by a mob in the center of Kabul. Farkhunda was violently beaten and set on fire after a local cleric accused her of burning a Qur’an. (Kabul, March 22, 2015) Paula Bronstein

The number of troops in Afghanistan was capped at around 8,400 under President Barack Obama – a significant drop from the 100,000 he deployed in 2011.

Some in the Pentagon have complained that the Obama White House’s troop management system prevented them from acting quickly, and obscured the true number of troops in the country. In some instances, the military would call in private contractors or temporary forces to avoid exceeding Obama-imposed troop limits.

Critics of Mr Trump’s plan, however, feel it represents the President’s growing leniency with the military.

As a private citizen, Mr Trump railed against the wars in Afghanistan and Iraq, calling them a “waste” of lives and money. As President, however, Mr Trump has increasingly deferred to military leaders in making strategic decisions.

The former businessman quickly agreed to launching an air strike on Syria in April, and subsequently handed over control of troop levels in both Syria and Iraq to the Pentagon.

Ned Price, senior director of the National Security Council under Mr Obama, added that the decision to deploy troops should be made in concert with political, economic, and development agencies – not just the military.

“Failing to do so can be a detriment to our strategic goals for the country or region in question and, in places where brave Americans are deployed, place our men and women in uniform at greater risk,” Mr Price told The Independent.

More than 2,300 Americans have been killed and more than 17,000 have been wounded in Afghanistan since the war began in 2001.