The US is to defy growing international pressure by going ahead with its military strike inside Afghanistan without seeking a specific mandate from the UN.

Failure to secure the support of the 15-member UN security council risks opening up a debate similar to that during the Kosovo war, where NATO went ahead without UN approval.

According to sources close to the UN security council, US diplomats have made no approaches at UN headquarters in New York seeking such a resolution.

The Russian President, Mr Vladimir Putin, has called for the US to give the security council a key role. France and Germany have also raised the issue. Mr Putin and the French President, Mr Jacques Chirac, agreed in a telephone conversation on Thursday that the Security Council should be at the centre of international efforts to battle terrorism, according to the Kremlin.

The prevailing view in Washington is that its planned action is sufficiently covered already by international law and does not need the added complication of going to the security council.

The US sees a strike against Afghanistan as covered by article 51 of the UN's founding charter that allows acts of self-defence: "Nothing in the present charter shall impair the inherent right of individual or collective self-defence if an armed attack occurs against a member of the UN, until the security council has taken measures necessary to maintain international peace and security. Measures taken by members in the exercise of this right of self-defence shall be immediately reported to the security council." The US will also point to a UN security council resolution passed within 80 minutes on the day after the New York and Washington attacks.

The security council expressed "its readiness to take the necessary steps to respond to the terrorist attacks of September 11th, 2001 and to combat all forms of terrorism, in accordance with the charter of the UN." A senior British Foreign Office source admitted this week: "That is not the same as a mandate." But the source added: "It is very strong and provides a huge amount of moral authority." The source said bluntly that whether the US would seek a further resolution depended on whether a draft would meet with favour in the security council. He said member states were entitled to act in self-defence as long as the response was proportionate.

At UN headquarters, a diplomat close to the security council said the US did not appear to want to return to the security council because that might "complicate" the international consensus being built up.

Although the Taliban has no supporters on the security council, the diplomat said there could be disagreement from some of the permanent security council members, either Russia or China or both.

There is a widespread feeling at UN headquarters and among European foreign ministries that the world organisation, if it does not discuss the military action, can have a role at a later date in helping to co-ordinate an international effort in the fight against terrorism.

After meeting the UN secretary-general, Mr Kofi Annan, on Thursday the German Foreign Minister, Mr Joschka Fischer, said: "This will be a long-term campaign and we have to tackle the problem of international terrorism on all levels - financial, political, intelligence, police, immigration, and, of course, also military.

"I think for all of this, you need a broad coalition, and the UN, especially Kofi Annan ... can play a very important role."

He echoed Mr Chirac, who said on Wednesday after meeting Mr Annan that the long-term battle against terrorism must go beyond military action.

It must strengthen the police, the judiciary and the military, target "the dirty money that finances terrorism" .

Opposition TDs attack Ahern airport offer

The Government's decision to offer the United States the use of Irish airports in any military campaign against Osama bin Laden was criticised early today by some opposition politicians.

Opening Irish airspace and airports to US was planes would hand the American military a "blank cheque" and fatally compromise neutrality according to the Green Party.

Their foreign affairs spokesman, Mr John Gormley, said the Taoiseach's offer, disclosed at the EU heads of government summit in Brussels and to be conveyed on Wednesday to the US Secretary of State, Mr Colin Powell, was "naive and foolhardy". Accusing the Government of arrogance, he said the Dail should have been consulted before Mr Ahern publicly allied himself to Washington's war on terrorism.

"It is quite incredible that the Government has agreed to let the US use our airports before they even know the nature of the military operation. The decision does not have the sanction of Dail Eireann," he said.

There was a danger that Islamic terrorists might regard Ireland and Irish citizens as legitimate targets should the Government back the US in a campaign against the Taliban, Mr Gormley said.

Mr Gay Mitchell, Fine Gael health spokesman and author of the party's policy document Beyond Neutrality, said Dail approval had been required when NATO forces landed and refuelled her during the Gulf War and during last year's bombing campaign in Kosovo.

However, he added that in the wake of the terrorist attacks on the World Trade Centre, opposition parties were likely to support the Government's stance.

The Socialist Party TD, Mr Joe Higgins, described the Taoiseach's actions as "craven and highly irresponsible".

"To offer the unconditional use of Irish airports will make this country an accessory to any or all of the strikes which may be launched and therefore guilty of contributory to the inevitable civilian casualties," he said.

Patrick Smyth in Washington adds: The reference by the Taoiseach to assistance being offered "in pursuit of Resolution 1368" is an important qualification - Ireland insists its involvement in all international security operations should be backed by a UN mandate.

Resolution 1368, agreed unanimously on September 12th by the Security Council, called on all states to "work together urgently to bring to justice the perpetrators, organisers and sponsors of the terrorist attacks and stresses that those responsible for aiding, supporting or harbouring the perpetrators, organisers and sponsors of these acts will be held accountable."

Ireland supported the resolution.