Russian presidential adviser Sergei Glazyev attends the opening day of the St.Petersburg International Forum in St. Petersburg May 22, 2014. REUTERS/Sergei Karpukhin ASTANA (Reuters) - An outspoken Kremlin adviser accused the United States on Thursday of trying to stoke a military conflict between Russia and European nations over Ukraine for its own economic gain.

Sergei Glazyev, an economic adviser to President Vladimir Putin with responsibility for ties with Ukraine, said the United States' economy and global standing had benefited in the past from wars in Europe.

"Now they (the United States) are unfurling a war in Ukraine, after organizing a coup and putting their own people in charge, to use Ukraine as a detonator against Russia and Europe," Glazyev told reporters in the Kazakh capital, Astana.

"There is growing chaos in Ukraine, and the chaos is increasingly acquiring the traits of a global catastrophe," he said before Russia, Belarus and Kazakhstan signed a treaty creating a new trading bloc.

Glazyev did not provide any evidence to support his comments but said unidentified foreign mercenaries had been seen arriving in Ukraine to fight pro-Russian armed rebels in the east.

His comments were characteristically confrontational for an adviser who has regularly staked out more radical positions than the Russian government or the Kremlin, which at times has distanced itself from his remarks.

The crisis in Ukraine, from which Russia has annexed the Black Sea peninsula of Crimea, has caused the worst tensions in relations with the West since the Cold War ended.

The United States has denied instigating events which forced the removal of Ukrainian President Viktor Yanukovich, described by Moscow as a coup d'etat, and says it wants a peaceful resolution to the crisis. Washington has denied reports about U.S. mercenaries operating in Ukraine and says there is evidence of Russian support for the rebels there.

Pro-Russian separatists shot down a Ukrainian army helicopter on Thursday, killing 14 soldiers including a general, as government forces pressed ahead with an offensive to crush the rebellion.

Glazyev said the situation in Ukraine was already a "de facto war".

"Any war in Europe results in great gains for America, in the strengthening of its geopolitical influence, and they are sticking to their tradition," he said.

Glazyev said Ukraine's newly elected president, Petro Poroshenko, could be considered legitimate only if he halted a military operation to flush out the rebels in the east.

"The only the thing he could undertake to legitimize his position, would be to stop the clearly illegal and inhumane operation in the southeast," he said.

(Editing by Raissa Kasolowsky)