The Arab-language television station, al-Jazeera, has broadcast a message said to be from Osama Bin Laden, in which he calls for Muslims to stand with the Iraqi people against the United States.

We stress the importance of martyrdom attacks against the enemy. These attacks inflicted on America and Israel a disaster they have never experienced before Voice identified as Osama Bin Laden

Click here for excerpts for Bin Laden message

The message was contained in a poor quality audio recording in which a man's voice, alleged to be Bin Laden's, is heard calling for suicide attacks against Americans and resistance to any attack on Iraq.

The tape's broadcast comes as diplomatic moves are continuing to resolve the diplomatic row between the US and Europe regarding the possibility of military action in Iraq.

The Bush administration believes the tape to almost certainly be genuine and officials say the message heralds a "burgeoning alliance of terror".

The broadcast came on the same day that the head of the CIA, George Tenet, warned of an increased risk of al-Qaeda attacks in the US and on the Arabian peninsula using a "dirty bomb" or poisons.

'Specific threats'

Many remain unconvinced by the veracity of the tape, citing the convenience of the timing - as tensions between the US and Europe continue regarding the Iraqi crisis and previous incidences of fakes.

BBC security correspondent Frank Gardner says it is also not strictly an admission of an al-Qaeda-Iraqi link, as the voice on the tape makes a clear distinction between the Iraqi people and the Iraqi regime.

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This, he says, is a distinction that the US administration has either failed or chosen not to see.

The tape revelation comes as Mr Tenet, at a US Senate committee hearing alongside Director of the Federal Bureau of Investigation Robert Mueller, said that US intelligence had pointed to possible terror in a matter of days, possibly involving chemical or nuclear weapons.

"The intelligence is not idle chatter on the part of terrorists and their associates," Mr Tenet said.

"It is the most specific we have seen, and it is consistent with both our knowledge of al-Qaeda's doctrine and our knowledge of plots this network - and particularly its senior leadership - has been working on for years."

The UK army has also begun maintaining a high profile presence at London Heathrow Airport in response to an increased security alert on orders from UK Prime Minister Tony Blair.

Diplomacy continues

Meanwhile Nato ambassadors are due to meet in Brussels on Wednesday to resolve continuing diplomatic tensions over Iraq.

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The crisis began when France, Germany and Belgium on Monday opposed Nato plans to begin shipping defensive equipment to Turkey - the only Nato member bordering Iraq.

Talks on Tuesday ended in deadlock, and BBC correspondent Chris Morris says there are no guarantees that this session will end with any firm results.

On Tuesday the US Secretary of State Colin Powell said that decision time was rapidly approaching for both Nato and the United Nations regarding Iraq.

Mr Powell was referring to Friday, when the UN's chief weapons inspectors, Hans Blix and Mohammed ElBaradei, are to make a crucial report on whether Iraq has been complying with disarmament demands.

A senior German Government source has said that 11 out of the 15 members of the United Nations Security Council support prolonging weapons inspections in Iraq.

Chinese President Jiang Zemin has added his support for more inspections in a telephone call to French President Jacques Chirac.

In other developments:

• The Russian parliament, or Duma, is to meet on Wednesday to debate the adoption of a statement proposing to veto any UN resolution authorising the use of force in Iraq

• Russian President Vladimir Putin ends a three-day visit to Paris, which has seen the Russian leader issuing a declaration, along with France and Germany, demanding increased weapons inspections in Iraq and a diplomatic solution to the crisis

• Australian Prime Minister John Howard, an ally of the US and UK position on Iraq, is due to meet UK Foreign Secretary Jack Straw in London on Wednesday

• Spain and Germany will enter the second day of a summit between the two countries which ended with little agreement on Iraq on Tuesday.