U.S. plans for a missile defense system in Europe were blocking its new nuclear arms reduction pact with Russia, Sky News reported Wednesday.

The world's biggest nuclear powers were due to sign a new Strategic Arms Reduction Treaty two and a half months ago.

Both sides insisted a breakthrough was close, but resetting relations between these old enemies was proving more difficult than U.S. President Barack Obama might have hoped.

Russia recently embarked on a campaign of military muscle flexing. It regarded America's missile defense plans in Europe as a threat, and threats must be countered with shows of strength.

Prime Minister Vladimir Putin said Russia must develop new offensive weapons to counter the proposed U.S. missile shield.

"You will see tactics of attack and shooting," a Russian general said.

"Our soldiers are equipped with new machine guns and we have new tanks. We are far more mobile than before."

Russia recently unveiled its first stealth fighter jet, the Sukhoi T-50, seen as a rival to the U.S. F-22 Raptor. Many of its capabilities remained secret, but the makers said it marked a significant increase in Russia's military effectiveness.

Such powerful images were welcomed after embarrassment over the repeated failure of Russia's new Bulova nuclear missile. The most recent test in December ended in an explosion that cast a spiral of white light over Norway, the seventh failure in 12 launches.

Russia welcomed Obama's scrapping of a Bush administration plan to deploy interceptor missiles in Poland and the Czech Republic.

But in what Russia called surprise moves, Bulgaria and Romania offered to host elements of a reconfigured U.S. missile shield.

Military analyst Alexander Pikayev questioned the timing of their offers.

"U.S. and Russian relations were improving, but these proposals really don't help the situation," he said.

"This situation is a time bomb. If these plans go ahead it could cause big problems in five to 10 years' time."

In a counter-move, Moldova's pro-Kremlin region of Trandniestra said it was ready to host Russian tactical missiles if asked.

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