The information pointed to possible suicide attacks on US interests in the Middle East and the most likely threat was against US targets overseas, Attorney General John Ashcroft told a news conference.

"The most recent intelligence that has prompted us to change our status has focused primarily overseas," Ashcroft said. "New information has fed into an analytic structure which has made us take very seriously both the new information and the analysis which leads us to this conclusion. Information has become available very recently."

He called on Americans to go about their business as normal and said US government workers would report for duty as scheduled today.

Vice President Dick Cheney cancelled a speech he was due to give on Tuesday night and would spend the night at a secure location, officials said.

The warning comes on the eve of the anniversary of the September 11 attacks on New York and the Pentagon that killed around 3 000 people.

Those attacks have been blamed on the al Qaeda network, headed by Osama bin Laden.

"We are now at high risk of a terrorist attack," Tom Ridge, White House homeland security adviser, told the news conference.

The change in threat level comes as Americans are already on edge, with opinion polls showing that many people expect fresh attacks against the United States.

The threat level has been raised to "orange," reflecting a "high risk of terrorist attacks" and is one step below the top "red" threat level, where the risk is seen as "severe."

The threat level has stood at "yellow," the middle of the five-point scale, since the government created the colour-coded system in March to offer people guidelines on how to prepare for any attacks after September 11.

The United States will close its embassies in Indonesia and Malaysia on Wednesday for fear of attacks. The embassy in Pakistan will also close.

The United States Navy has released a warning to shipping in the Middle East Gulf against possible planned attacks by al Qaeda against oil tankers. - Nampa-Reuters

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