Washington earlier this week received Ilyas Akhmadov, who identifies himself as the Chechen foreign minister.

This latest diplomatic row comes amid growing international pressure on Russia for its campaign in the republic.

Federal forces are accused of using excessive force, and the relief agency Medecins Sans Frontieres has accused Moscow's forces of war crimes.

The plight of Chechnya's civilians in the war was raised again on Friday when a delegation from the Council of Europe held talks in Moscow.

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Moscow is showing few signs of bowing to pressure from the international community - rather it appears to have gone on the diplomatic offensive and is flexing its muscles.

On Friday acting President Vladimir Putin approved a security policy paper which makes it easier for Moscow to press the nuclear button.

The new national security document envisages the use of nuclear weapons if Russia has to repel armed aggression when all other means of resolving the crisis have been exhausted.

Our correspondent in Moscow, William Horsley, says the concept underlying the doctrine is clear: that the US must not be seen as the world's only superpower.

'Foreign minister's' visit

Russian Foreign Minister Igor Ivanov had strong words for the Americans on Friday following the visit of Mr Akhmadov to the US.

"We have more than once announced that this type of action implies support for terrorism and separatists, and not only in Russia," he said.

Moscow says that Mr Akhmadov has no right to go by the title of foreign minister.

Washington has said that the Chechen was received as a private citizen and not as a diplomatic envoy.

Council of Europe criticism

In Moscow, Irish Foreign Minister David Andrews said that Russian actions in Chechnya were in violation of commitments it had made to become a member of the Council of Europe.

Mr Andrews, who chairs the committee of ministers at the council, said he had urged Moscow to halt its military campaign during his talks with Mr Ivanov.

"This crisis has become the focus of widespread concern, including among the members of the Council of Europe," he said.

He described the talks with Mr Ivanov as "frank and at times robust".

"I urge that all hostilities should cease and only then can Russia meet its obligations as a member of the Council of Europe," said Mr Andrews.

Russia opens border

On the ground in Chechnya, Russian forces have now lifted their ban on most Chechen men and boys - aged 10 to 60 - from crossing the border with Ingushetia.

The travel ban was imposed two days ago after rebel fighters carried out successful counter attacks on federal forces.

The closure of the border was strongly criticised at home and abroad.

Moscow's forces have continued their thorough searches of towns and villages in territory under their control.

A BBC correspondent in Moscow, James Rogers, says that although they vastly outnumber the Chechen rebels, Russian forces face the continuing threat of counter-attack from fighters that have evaded their searches.

The Russian Defence Ministry on Friday vehemently denied reports of growing Russian casualties in the campaign. It described the reports of higher casualties as "conscious lies".

The defence ministry also announced that Russian fighter planes and gunships continued to bombard rebel targets in Grozny, and in the mountains in southern Chechnya.

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