Shortly afterwards, at around midnight (0000 GMT), the Dart 8 cargo vessel, which had been loading equipment throughout the day, left the port for Asia where it will support thousands of British troops marshalled for a possible conflict with Iraq.

"The Dart 8 is in the process of sailing now," a Defence Ministry spokesman told Reuters. "She was scheduled to leave at 10 p.m. (2200 GMT), so she has been delayed by about two hours."

The Rainbow Warrior had been anchored at the entrance to Marchwood since Monday as part of Greenpeace's campaign to stop ships heading to the Gulf.

The government had ordered it to move on Saturday and when those orders were ignored, some 20 police officers boarded the ship and took control of it, attaching it to the tug and cutting it free from its mooring.

The Defence Ministry spokesman said the operation had not been opposed by around 20 Greenpeace activists on board and that the matter was now in the hands of the port authority.

On Friday, the government failed to get an injunction stopping Greenpeace from blocking the port but did obtain a limited ruling preventing the activists from boarding or touching ships chartered to carry military supplies.

Earlier on Saturday a government spokesman said the blockade had made it difficult but not impossible to load the Dart 8.

Prime Minister Tony Blair met U.S. President George W. Bush at the White House on Friday for what many saw as a council of war. Both insist Iraq is hiding weapons of mass destruction from U.N. weapons inspectors and must disarm voluntarily or be disarmed by force. Iraq says it has no such weapons.

U.S. Secretary of State Colin Powell is due to present to the Security Council on Wednesday what he says is compelling evidence that Iraq is concealing weapons programmes from the U.N. inspectors.

Chief weapons inspector Hans Blix, who said on Monday that Iraq was hampering investigations and listed a range of weapons still unaccounted for, is due to present a further report on his team's findings on February 14.

- Additional reporting by Astrid Zweynert and Jeremy Lovell.