Shortly before a ceremony in the US officially extending Nato's borders (640 km) 400 miles eastwards, the Russian foreign ministry warned that the expansion would produce new dividing lines in Europe.

"Russia's view of Nato enlargement has not changed and remains negative," the foreign ministry said in a statement

Many people fear that Nato expansion will divide Europe

In the Kremlin the Defence Ministry's head of international relations told reporters he believed the enlargement of Nato to be "a dangerous and historic mistake which could have serious consequences."

Colonel-General Leonid Ivashov said: "European history convincingly shows that as soon as the balance of forces are upset on the continent, the result is instability in political processes, conflicts and wars.".

But he said Russia would continue to co-operate with the alliance under the 1997 Nato-Russia Founding Act.

'Sad event'

"Russia agreed to co-operate with Nato and is developing that co-operation," he said. "But it's a two-way street."

Earlier in the week Foreign Minister Igor Ivanov said Moscow regarded the development as "a sad event" and "a movement in the wrong direction".

"All European states must co-operate in creating a joint security system," he said. "All European states must work together in the interests of all countries rather than of separate groups."

On Friday the Belarus President, Alexander Lukashenko, added his concerns at the alliance's eastward expansion and repeated his call for Ukraine to join Belarus and Russia in a pan-Slavic bloc.

Shared border

Speaking in the Ukrainian capital, Kiev, at the start of a two-day visit, Mr Lukashenko said Belarus would consider strengthening its armed forces now that it shared a border with a Nato member.

"We have to take into account that our border with Poland has become a border with NATO," he said

But he added he would not press Ukraine's President Leonard Kuchma to join an alliance to counter the influence of Nato.