Gordon Brown believes that Britain should remain an “honest broker” in negotiations over Georgia's membership of Nato, despite increasing pressure from the US for the country to join the alliance.

Mr Brown refuses to match American rhetoric over Tbilisi's efforts to win Membership Action Plan (MAP) status — the first step towards membership. He believes that forcing a split within Nato would be counter-productive.

Britain failed to give full support for Georgia's application at the Nato council in Bucharest in April and is set to maintain the position at the next key meeting this November, according to senior British diplomats.

Candidate countries such as Macedonia — which was given MAP status earlier this year — are set a timetable and conditions prior to full membership.

But Georgia, together with Ukraine, was turned down despite heavy pressure from Washington.

British diplomats insist that the UK shares Georgia's Nato objective and disagrees with the US only over the means to secure it, pointing out that full consensus is needed to secure membership.

One aide said that Mr Brown and David Miliband, the Foreign Secretary, believed that Nato unity was more important than the aspirations of any one candidate state.

Privately, senior figures caution against handing Russia the diplomatic prize of open squabbling between countries such as Germany — which is extremely cautious over Georgia's membership — and supporters such as the Baltic states and the US.

With ever more strident calls for the country to be given a formal timetable, Mr Brown's efforts to avoid taking sides in the dispute become more difficult, however.

The Prime Minister must decide soon whether he should represent Britain in person at the North Atlantic Council meeting this November . If he fails to attend, critics are likely to accuse him of hiding from one of the most difficult foreign policy decisions he has yet faced.

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