British spy chiefs feared US invasion of Saudi Arabia, Kuwait in 1973.

(From Agence France Presse)

British spy chiefs secretly warned that the United States would be prepared to invade Saudi Arabia and Kuwait to seize their oilfields following the 1973 Arab-Israeli war, it was disclosed.

Files released to the British National Archives under the 30-year rule for classified documents show the intelligence agencies believed the US was ready to take military action to prevent further disruption to oil supplies.

It followed the decision in October 1973 by the Arab nations to slash oil production, and send prices rocketing, while imposing a complete embargo on the Americans over their support for Israel.

In Britain, Prime Minister Edward Heath's Conservative government, which adopted a more pro-Arab line, was forced to draw up plans for gasoline rationing after panic buying led to shortages at filling stations.

Although the war in the Middle East was over after three weeks, a secret assessment drawn up for government ministers by the Joint Intelligence Committee (JIC) -- including the heads of MI5 and MI6 -- concluded the US would rather risk military action than be held to ransom again by the Arabs.

The report, dated December 12, 1973 and marked "UK Eyes Alpha", described the seizure of the oil-producing areas in the region as "the possibility uppermost in American thinking".