Under pressure: Robertson

Downing Street has admitted that the NATO row over military protection for Turkey is a "serious" matter.

The prime minister's official spokesman admitted that the decision by Germany, France and Belgium to block plans to place anti-missile defence systems on Turkey's border had created difficulties, but claimed it did not mean NATO was finished.

"We're not saying it's not serious because it is," said the prime minister's official spokesman.

"Clearly agreement would be preferable to what we have at the moment but to write off NATO on the basis of what's happened over the last 48 hours is wrong.

"We shouldn't go from the fact that there is a difference to saying that NATO has no relevance and writing the institution off."

Officials had earlier tried to play down the significance of the decision.

"No-one actually vetoed anything. The breaking of silence allows further discussion to take place and that's what will take place," said Downing Street on Monday.

"It's likely this is going to be a matter of continuing conversation."

Following the decision of the three countries to block the bid, the Turkish government requested renewed discussions under self-defence treaty articles.

Discussions on the dispute are continuing in a bid to reach agreement and prevent the crisis growing.

The row is set to further damage relations between Paris and Washington, following the announcement of a Franco-German plan to boost inspections by increasing the number of UN staff in Iraq.

Belgian officials said sending the missiles would "send the wrong signal" at a crucial time.

However, experts are warning the row could cause irreparable damage to the transatlantic alliance.

Last week the NATO chief sought to call the bluff of objectors by initiating a "seven day silence" procedure in which members had a chance to object to the measure before it was approved.

But the three European governments angered Washington by blocking help for Turkey.

The US administration has slammed the move as "shameful and inexcusable".

British defence minister Adam Ingram told the Commons on Tuesday that NATO was still one of the cornerstone's of British defence policy.

Conservative shadow defence minister Bernard Jenkin claimed the roots of the crisis were in the 1998 St Malo directive agreed between France and the UK.

He accused ministers of "aiding and abetting France's ambition to destroy NATO".