(Recasts with British minister, NATO general)

By Stephen Brown and Noah Barkin

MUNICH, Feb 6 (Reuters) - European defence officials warned on Friday that arming Ukraine in its fight against pro-Russian separatists would only inflame the conflict, but were told by NATO's top soldier, an American general, that the West should consider using "all tools" if diplomacy with Moscow wasn't working.

The debate at the Munich Security Conference highlighted an emerging rift between Europe and Washington over how to confront Russian President Vladmir Putin as Moscow-backed rebels make territorial gains in eastern Ukraine.

President Barack Obama is under pressure from some in Congress to provide Kiev with lethal weapons.

German Defence Minister Ursula von der Leyen voiced Europe's misgivings about this strategy: "Are we sure we would be improving the situation for the people in Ukraine by delivering weapons? Are we really sure that Ukraine can win against the Russian military machine?"

"And would this not be an excuse for Russia to intervene openly in the conflict?" asked the German minister.

Britain also fears that sending weapons could "escalate the conflict", her British counterpart Michael Fallon told the conference.

As they spoke, Chancellor Angela Merkel and French President Francois Hollande held talks in Moscow with Putin to try to end the conflict in Ukraine that has killed more than 5,000 people and driven Russia's relations with the West to new lows. Their initiative was partly prompted by the debate about arming Kiev.

NATO's top military commander, Gen. Philip Breedlove, gave the strongest indication so far that he is - as the New York Times reported this week - among the U.S. officials who favour providing defensive arms and equipment to Ukraine's military.

The West has tried using diplomatic and economic measures to put pressure on Putin, he said. "But if what is being done is not producing what you want to gain from the conversation, then maybe all tools in the tool bag should be used and conventional means should not be outwardly discounted," Breedlove added.

Germany's von der Leyen questioned the strategic sense of providing weapons to Kiev when the separatists were so well-supplied by the Russians.

"The support with arms from Russia to the separatists is potentially unlimited," she said. "And do we really count on being able to provide as many arms to the Ukrainian army that they could potential conquer the other side?" (Additional reporting by Adrian Croft)

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