NATO Secretary-General Anders Fogh Rasmussen says he has seen no evidence that Russia is withdrawing troops it deployed along Ukraine's eastern border.
Rasmussen was speaking in Brussels ahead of a NATO foreign ministers' meeting on April 1 to discuss Ukraine, where Russia has annexed Crimea and continues to refuse to recognize the authority of the government in Kyiv.
"Unfortunately, I cannot confirm that Russia is withdrawing its troops," Rasmussen said, one day after the Russian Defense Ministry said it was withdrawing a motorized infantry battalion from a region near the border. "This is not what we are seeing. And this massive military buildup can in no way contribute to a deescalation of the situation, a deescalation that we all want to see."
Rasmussen said that Russia's "aggression against Ukraine...fundamentally changes Europe's security landscape and it causes instability right on NATO's borders."
Rasmussen also said Russia had undermined the principles which represent the foundation of the NATO-Russia partnership, and that as a result there could be no more "business as usual."
"We will make clear that Russia's actions are unacceptable," Rasmussen said. "We will take decisions on which cooperation with Russia is still appropriate because through its actions Russia has undermined the principles on which partnership is built and has breached its own international commitments. So we cannot go on doing business as usual."
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The NATO meeting in Brussels is the first since Russia's military occupation late last month and annexation a week ago of Ukraine's Crimea region.
Speaking at the opening of the meeting, Rasmussen said Moscow's actions had "undermined the foundations" of the NATO-Russia partnership.
"Today we will discuss how to safeguard security and stability in the Euro-Atlantic area because Russia has shown that it is ready to use force to redraw borders and recreate dividing lines in Europe," he said.
Russia in the past month massed tens of thousands of troops on its border with Ukraine, raising concerns that after annexing Crimea it might invade other parts of Ukraine.
On March 31, the Russian Defense Ministry had said it was withdrawing a battalion that had ended what it says were routine military drills near the border.
NATO has ruled out military intervention in Ukraine -- which is not a member of the military alliance -- but has scrambled to reassure NATO's members in Eastern Europe, especially the Baltic states.
On April 1, Rasmussen said that ministers would adopt the necessary measures to deter any threat against NATO's allies and offer support to Ukraine.
"This crisis shows again that we cannot take security and stability in the Euro-Atlantic area for granted," he said. "This is why we need to enhance our ability to operate together as allies and with partners. And we need to provide more help to others to build-up their own defense capacities."
After convening in Brussels, the ministers of the 28 alliance member states later met with Ukraine's acting foreign minister, Andriy Deshchytsya, to discuss deepening cooperation between NATO and the new authorities in Kyiv.
Ukraine's parliament on April 1 approved conducting military exercises with NATO countries.
Russia warned Ukraine on April 1 against integration with NATO, saying Kyiv's previous attempts to move closer to the bloc had strained Russia-Ukraine relations, caused problems between NATO and Russia, and a split in Ukrainian society.
In a statement, the Russian Foreign Ministry cautioned that future economic ties between Moscow and Kyiv "will largely depend on the actions Ukraine takes in its foreign policy."
With reporting Reuters and AP