President Donald Trump committed U.S. troops to an open-ended war in Afghanistan, a decision the Afghan government welcomed on Tuesday but which Taliban insurgents warned would make the country a "graveyard for the American empire".

Trump offered few specifics in a speech on Monday but promised a stepped-up military campaign against the Taliban who have gained ground against U.S.-backed Afghan government forces. He also singled out Pakistan for harboring militants in safe havens on its soil.

Trump, who had in the past advocated a U.S. withdrawal, acknowledged he was going against his instincts in approving the new campaign plan sought by his military advisers but said he was convinced that leaving posed more risk.