Mr Cook announced on Saturday that the UK was suspending all national arms exports to Indonesia.

He declared the ban as he halted a proposed shipment to Indonesian capital Jakarta of nine British-made Hawk jets.

Britain has also sent a detachment of 250 Gurkha troops from the 2nd Battalion Royal Gurkha Rifles to nearby Brunei.

The BBC's Jon Kay: "Other countries are likely to follow suit"

The troops are on standby to act as part of a UN peacekeeping force in the stricken territory if requested.

Tens of thousands of East Timorese are reported to have been killed in the past week, amid violence by pro-Indonesian militiamen following a referendum in favour of independence for the territory.

Government attacked

Former Liberal Democrat leader Paddy Ashdown accused the government of being "shamble footed" in its handling of the crisis.

He told the BBC's Breakfast With Frost programme it was "shameful" that lessons from the Kosovo conflict had not been learned.

"We cannot go on doing this, allowing these things to develop because of a lack of action at an earlier time and then paying a price in lives and a lack of respect for international law in the long term," he said.

U-turn on Hawk contract

Mr Cook's announcement of the arms ban came just hours after the Ministry of Defence in London had confirmed that the consignment of Hawks would be delivered to Indonesia.

Foreign Secretary Robin Cook: "Britain will support an EU arms embargo"

The change of heart followed a visit to East Timor by the British ambassador to the UN.

Mr Cook said in a statement: "I have spoken to our ambassador to the United Nations, Sir Jeremy Greenstock, who has returned from the visit by the UN mission to East Timor.

"Sir Jeremy was shocked by what he saw. He told me that Dili had been burned down and that tens of thousands of refugees are facing starvation in the mountains."

Violence is continuing in East Timor

Mr Cook said: "Britain will be supporting on Monday a proposal by the European Union for an arms embargo.

"We are taking action on a national level to suspend all arms exports to Indonesia.

"It is right that we should bring home to the Indonesian army the horror of the world at the brutality that they have visited on East Timor."

'Embarrassing' change of heart

Shadow defence secretary Iain Duncan Smith said the government had delayed "for days" while the crisis worsened and had been forced to act by the Americans.

Robin Cook: About turn "not in the least embarrassing"

He said: "I don't think the government had any plan at all."

The deal for the jets was signed by the Conservative Government in the 1980s.

Indonesia already owns more than 40 of the British-made aircraft.

Mr Cook denied that suspending the sale of the jets was embarrassing for the government.

"It's not in the least bit embarrassing. They were licensed by the previous administration," he said.

"Nobody has ever found any military equipment licensed by this government that has turned up in East Timor, nor will they."

Clinton suspends sales

The UK move follows the United States' suspension of military sales to Indonesia, designed to put more pressure on the government to allow UN peacekeepers into East Timor.

President Clinton: Turning up the heat on Indonesia

President Bill Clinton announced the move on the eve of an Asia-Pacific summit in Auckland, New Zealand.

He said increasing the pressure on Indonesia could help "persuade the Indonesians to support the UN operation to go in and help end the violence and secure the safety of the people there."