By Roger Hardy BBC Middle East analyst

All of Washington's Arab allies are nervous about the Bush administration's determination to topple the Iraqi leader, Saddam Hussein.

But none are more apprehensive than King Abdullah of Jordan.

Abdullah has warned the west about attacking Iraq

He has warned the United States that an attack on Iraq would open a "Pandora's Box" in the Middle East.

The king goes on to Washington later in the week for talks with President Bush to express his anxiety.

Jordan is highly sensitive to events in the Israeli-Palestinian arena since some 60% of its people are of Palestinian origin.

Any use of Jordanian territory might therefore spark a backlash.

So concerned were officials by reports of military co-operation with the Americans that they recently invited foreign journalists to visit an air base near the Iraqi border, to show them that no unusual activity was taking place.

Equally, no Arab leader wants to be seen helping the United States at a time when it is perceived to be giving unquestioning support to Israel, and at a time when the situation in the West Bank and Gaza has deteriorated so badly.

Plans of attack

In an interview on American television, King Abdullah said: "Trying to take on the question of Iraq with the lack of positive movement on the Israeli-Palestinian, Israeli-Arab track seems, at this point, somewhat ludicrous."

As they ponder alternative plans of attack, US policy-makers see Jordan as an attractive asset.

To attack Iraq from the south, they would need bases in one or more of the Gulf Arab states. To attack from the north, they would need Turkey. To attack from the west, they would need Jordan.

Israel also sees the Jordanian kingdom, situated between itself and Iraq, as a natural buffer zone.

The Israelis fear that, in retaliation for an American attack, Saddam Hussein might launch Scud missiles at them.

But from Jordan's point of view, a new regional war would present huge risks. Jordanian public opinion is already strongly anti-American, because of Washington's support for Israel and the continuation of UN sanctions against Iraq.

Opinion might become dangerously inflamed in the event of an attack.

A crisis over Iraq could inflict great economic as well as political damage. Some analysts even think Jordan might implode.

Testing times

Three years after succeeding his father, King Hussein, to the throne, the 40-year-old Abdullah is now finding himself tested to the limit.

He is haunted by his father's fateful decision to side with Iraq during the Gulf crisis of 1990. This enabled him to hold his kingdom together, but at the price of alienating the United States.

A similar choice now confronts King Abdullah, but in the changed circumstances resulting from the 11 September attacks of last year.

He cannot ignore pressure from the American superpower. But neither can he ignore the anger of his own people.