Yugoslav President Slobodan Milosevic, right, shakes hands with Russian Foreign Minister Igor Ivanov in Belgrade

BELGRADE, Yugoslavia (CNN) -- Russia and Yugoslavia on Sunday warned against possible NATO intervention over the Kosovo conflict, saying such a move would have "immeasurable and lasting consequences."

Russian Foreign Minister Igor Ivanov and Defense Minister Igor Sergeyev met Yugoslav President Slobodan Milosevic to discuss the growing threat of NATO strikes to punish Belgrade over the Serbian crackdown in the Kosovo province.

The talks in Belgrade came on the eve of a pivotal report from U.N. Secretary-General Kofi Annan, who was to judge whether Yugoslav authorities have sufficiently complied with a U.N. Security Council resolution demanding an end to the crackdown and calling for committed peace talks.

If not, NATO may see a green light to strike on its own.

The Yugoslav news agency Tanjug said Moscow and Belgrade agreed that "foreign military intervention would represent an act of aggression against Yugoslavia with immeasurable and lasting consequences on international relations."

Tanjug also carried a statement by Yugoslavia's Supreme Defense Council, which is headed by Milosevic. The statement said that the country would defend itself by "all means available" against NATO air attacks.

Milosevic, right, talks with a Russian delegation

Parallel to the Belgrade talks, the Russian government Sunday also issued a statement against NATO intervention.

"The Russian government thinks it necessary to emphasize again that using force against a sovereign state without the sanction of the Security Council would be a rude violation of the U.N. charter," the statement said.

Moscow urged both sides in the Kosovo conflict to honor U.N. resolutions on ending the fighting, restarting talks and averting a humanitarian disaster for refugees huddling in forests with a frigid winter coming.

NATO has grown more bellicose toward Belgrade in recent days, while acknowledging that the Yugoslav side has begun to bend before the diplomatic firestorm by appearing to pull significant armored combat forces out of Kosovo.

U.S. Defense Secretary William Cohen said on Friday that air strikes could occur within two weeks if Milosevic did not remove forces responsible for devastating ethnic Albanian communities and driving 300,000 people from their homes.

After months of hesitation, Western powers rediscovered their resolve to call Milosevic to account after reports began to emerge a week ago of massacres of ethnic Albanian civilians -- including women and children -- allegedly carried out by Serbian troops.

The Russian government's statement insisted Western intervention could not solve the sort of deeply rooted ethnic conflict unfolding in Kosovo.

Russia is a traditional Slav Orthodox ally of Serbia. Russia and China dispute Western claims that resolutions the Security Council has already passed authorize the use of force by NATO without the need for a further vote.

Britain, meanwhile, was planning to deploy several thousand ground troops and tank units in Kosovo following a NATO bombardment, The Sunday Telegraph reported.

However, Defense Secretary George Robertson refused to confirm or deny the report.

He reiterated that Britain was ready to take part in a NATO attack, saying "cat and mouse tactics" by Milosevic were unacceptable.

The Associated Press and Reuters contributed to this report.