Further Russian intervention in Ukraine, following its annexation of Crimea, would be a "historic mistake" that would deepen Russia's international isolation, NATO Secretary-General Anders Fogh Rasmussen said on Wednesday.
"If Russia were to intervene further in Ukraine, I wouldn't hesitate to call it an historic mistake," he told a news conference after a meeting of alliance foreign ministers.
- Ukraine in crisis: Key facts, major developments
- ANALYSIS | Among Ukraine's young, disappointment runs high: Nahlah Ayed
"That would lead to further international isolation of Russia. It would have far reaching consequences for the relations between Russia and … the Western world. It would be a miscalculation with huge strategic implications."
Earlier Wednesday, NATO's top military commander said Russia has all the forces it needs on Ukraine's border if it were to decide to carry out an "incursion" into the country and it could achieve its objective in three to five days.
Calling the situation on the border "incredibly concerning", NATO's Supreme Allied Commander Europe, U.S. Air Force General Philip Breedlove, said NATO had spotted signs of movement by a very small part of the Russian force overnight but no indication that it was returning to barracks.
NATO foreign ministers meeting in Brussels had asked him to draw up by April 15 a package to reassure nervous NATO allies in eastern Europe that would include reinforcements by land, air and sea, he said in an interview with Reuters and The Wall Street Journal.
Meanwhile, Russia accused NATO on Wednesday of reverting to the language of the Cold War by suspending cooperation with Moscow, and said neither side would gain from the move.
NATO suspended all practical co-operation with Russia on Tuesday in protest at its annexation of Crimea from Ukraine, and ordered military planners to draft measures to strengthen its defences and reassure nervous eastern European countries.
Russia also increased pressure on Ukraine to disarm paramilitary groups, urging it to go beyond "sham" promises to crack down on the far-right and protect Russian speakers.
Moscow also expressed concern that the Ukrainian government was not holding a public debate on plans to reform the constitution, making clear it fears the interests of the Russian-speaking community will not be taken into account.
Ukraine's parliament on Tuesday ordered security forces to disarm illegal armed groups and police shut down the Kyiv base of a far-right nationalist group, Right Sector, after a shooting incident in which three people were wounded.
"The fact that gunmen from the Right Sector have, so to say, vacated their headquarters in central Kyiv has received a lot of comment in Kyiv over the recent days," a Russian Foreign Ministry statement said.
It urged the Ukrainian authorities "not to confine themselves to 'sham' statements to fight radical forces in Ukraine but to take resolute measures to disarm gunmen."
Relations between Moscow and Kyiv have been in crisis since the Ukrainian parliament deposed Moscow-backed President Viktor Yanukovych on Feb. 22 and Russia seized control of the Crimea region from Ukraine before annexing it on March 21.
Yanukovych recants on Crimea
In other developments Wednesday:
- Ukraine's ousted president, Viktor Yanukovych, said he was "wrong" to invite Russian troops into Crimea, and vowed to try to persuade Russia to return the Black Sea peninsula. In his first interview since fleeing to Russia in February, he said he hopes to negotiate with Russian President Vladimir Putin to return the region he annexed in March.
Russians sanctioned by the European Union — 33 politicians and security officials — will be barred from new business interests in Switzerland, but billionaires included on the U.S. sanctions list face no restrictions, the Swiss government said. Switzerland decided last week against imposing its own sanctions in response to the Ukraine crisis, but promised not to become a place to circumvent sanctions imposed elsewhere.