LONDON - Britain refused on Wednesday to rule out using armed forces to rescue 170 Britons stranded in the Libyan desert after an appeal for help by desperate oil industry workers.

Britain's coalition government, facing politically damaging criticism from stranded Britons and opposition politicians that it had been slow to respond to the crisis, announced a review of its arrangements for air evacuations.

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"We need to know whether today was a coincidental series of unavoidable setbacks, or a systemic flaw," Foreign Secretary William Hague said in a statement.

British oil worker James Coyle -- one of 300 people including 90 Britons stranded at a camp in eastern Libya -- appealed to London earlier to rescue them, saying armed villagers had stolen their vehicles and most of their supplies.

"We are living every day in fear of our lives as the local people are armed ... We're living a nightmare here," Coyle said in a telephone interview with BBC radio from a camp in the Amal desert region of eastern Libya.

There are about 500 British nationals in Libya including 170 workers in various desert camps. About 300 are in the capital and 70 in the eastern city of Benghazi.

The revolt is threatening Muammar Gaddafi's 41-year rule. Much of eastern Libya is now in the hands of anti-Gaddafi protesters. Violence and looting have been reported in some areas.

Military options

Hague refused to discuss whether Britain could use military means to rescue the stranded Britons. "It would not be wise for me to set out all the options on this," he told the BBC.

Earlier, Hague said he did not rule out Britain sending military flights into Libya without Libyan permission to evacuate stranded British nationals.

Asked if Britain would support military action to halt violence in Libya if there was international backing for such action, junior Foreign Office minister Alistair Burt echoed US Secretary of State Hillary Clinton by saying "all options are on the table."

Facing criticism of the evacuation plan, Hague postponed a planned visit to Washington on Thursday for talks with Clinton.

He pledged to send as many planes as necessary to bring back British nationals. But the first chartered plane bound for Tripoli was delayed for hours at London's Gatwick airport with a fault before it finally took off in the evening.

Later, the Foreign Office said it had found a chartered plane in Tripoli and that most Britons waiting at the airport there were boarding it. A number of other planes were expected to arrive in Tripoli overnight to pick up Britons, it said.

A British Navy frigate, HMS Cumberland, was due to arrive off Libyan waters on Wednesday night and could be used to evacuate about 70 British nationals from Benghazi, British officials said.

The BBC said a plane chartered by oil company BP had arrived in Libya to pick up employees of the firm.

BP, which has been preparing to start drilling in western Libya, refused to confirm the report. It said it had been evacuating staff and dependants since the start of the week.