US President Donald Trump announced yesterday that he was raising the military budget to defend the United States in his speech on the 18th anniversary of the September 11 attacks.

"We do not seek to engage in conflicts, but we will respond strongly if the United States is attacked," Trump said.

"If they return to our country for one reason or another, we will go where they are and use a military force that has never been used by the United States in history. I am not talking about nuclear power here," he said.

He warned that what he describes as an unprecedented US military offensive against the Taliban in Afghanistan would continue, just five days after peace talks with the group were canceled.

Trump said US forces "have hit our enemy more aggressively in the past four days than they have been and will continue to do so." He said the order was launched after he canceled secret peace talks with the Taliban over the weekend in response to an attack that killed a US soldier last week.

A US flag was planted on the western wall of the Pentagon yesterday to mark the 18th anniversary of the attacks on the United States.

Nearly 3,000 people were killed when hijacked planes crashed into the World Trade Center and the Department of Defense and a plane crashed into a field in Pennsylvania on September 11, 2001.