The hold-up in the departure of two plane-loads of Russian troops bound for Kosovo has exposed the continuing tensions between Moscow and Washington over the troops' deployment.

The Americans say the Russians are going against an agreement reached two weeks ago in Helsinki, both in relation to where the troops are to be sent in Kosovo, and over the command structure of the joint force.

The agreement over the Russian deployment was meant to show that matters were getting back on track.

This was emphasised by the Russian President, Boris Yeltsin, when he met his US counterpart, Bill Clinton, at the G8 meeting in Cologne.

But despite the smiles then, Russia's anger at Nato's policy over Kosovo may not be so easily calmed.

Signs of strain

Last week, in an incident reminiscent of the Cold War, two Russian bombers had to be escorted out of Icelandic air space by US fighters.

And a US military attache has been expelled from Moscow after being declared persona non grata - a diplomatic nicety implying espionage.

In the light of these incidents, perhaps some disagreement over the sending of Russian troops to Kosovo was to be expected.

The Americans say the Russians want to deploy their forces in areas others than those designated in the agreement reached at Helsinki.

They also accuse the Russians of refusing to comply with the clause which puts Russian forces in Kosovo ultimately under the command of Nato.

The Americans have been able to block the Russian deployment for the time being by persuading Hungary - now, of course, a Nato ally - as well as Romania and Bulgaria, to refuse permission for the Russians to use their air space.

This may well prove to be no more than diplomatic shadow boxing. But it does illustrate that Russo-American relations are still no better than cool.