WAS it a mistake, or a piece of pre-emptive one-upmanship by the Russians? Or simply a fresh indication of the fragility of the peace in Kosovo? When a column of 20 to 30 Russian military vehicles rolled into the Kosovo capital of Pristina on Friday, Nato was taken aback. The White House, we are told, was stunned and bewildered after having been assured by Moscow that its troops would not move in until they got the green light from the allies. Yesterday, the Russian Foreign Minister called the action a mistake, and Washington accepted that - but then the Interfax news agency in Moscow reported that the movement of Russian troops into Kosovo was agreed 'at the highest level'.
Whatever the truth, the alarm shows just how sensitive relations are between Nato and the Russians. Having played a key role in brokering the agreement which ended the bombing of Yugoslavia and opened the way for the return of the refugees, Moscow is intent on asserting the big power status which has so often escaped it in recent years.
That inevitably creates a major problem. Russia is unlikely to accept any arrangement that puts its troops under Nato's command. Equally, having forced President Milosevic to yield, Nato is not going to let the Russians, with their attachments to the Belgrade regime, set up a zone under their own control.
Moscow would probably like to set up such a zone in the north of Kosovo along the border with Serbia. That would be a grave setback for Nato and for the future of Kosovo, creating a safe haven for Serbs and a no-go area for returning ethnic Albanians.
On top of all the other complications in Kosovo, Nato now has to face the unpredictability of Moscow. President Yeltsin is becoming an ever more capricious figure by the day; his prime minister is new and lacks both stature and experience; the Government is factionalised; parts of the army seem to have a mind of their own.
All that would be a recipe for grave concern at the best of times. The danger is that the problem of Kosovo will also now become a problem of Russia. President Clinton needs to keep matters on the rails in his telephone discussion with his opposite number in the Kremlin today and, if necessary, to take the radical step of deciding that, after all, there is no place for Russia among the forces streaming into Kosovo.