ANKARA 

Hundreds of U.S. paratroopers have begun a controversial military mission with Ukrainian national guard forces amid criticism from Russia and pro-Russian separatists.

About 300 paratroopers and Ukrainian troops began the six-month operation dubbed Fearless Guardian on Monday, with Ukrainian President Petro Poroshenko claiming in a speech at the International Peacekeeping and Security Center in Lviv region that the mission "should facilitate the establishment of peace".

Poroshenko said the program would be joined by partners from Canada, Great Britain, Poland, and other NATO countries and Australia.

The paratroopers from the 173rd Airborne Brigade arrived at Ukraine's International Peacekeeping and Security Center in the western city of Yavoriv on April 14 and 15 and are to train three battalions of Ukrainian national guard soldiers, U.S. military officials have said.

Moscow and pro-Russian separatists in Ukraine say the U.S. presence destabilizes the situation in the conflict region and violates the Minsk cease-fire agreement agreed between Kiev and separatists in February, which involves the pullout of heavy weapons and political reforms in the eastern regions.

Dmitry Peskov, a spokesman for Russian President Vladimir Putin, said: "The presence of foreign instructors in Ukraine, where an internal conflict remains unresolved in southeast and where problems arise with the implementation of the Minsk peace agreement, does not help in settling the conflict and producing an environment beneficial for it.

"On the contrary, it destabilizes the situation."

'Minsk deal violated'

Separatist leader of the self-proclaimed Donetsk People's Republic, Denis Pushilin, also said the arrival of the U.S. paratroopers would make the situation even worse in addition to violating the Minsk agreement.

"The arrival of U.S. military instructors in Ukraine will aggravate the situation in Donbass. It is a violation of Minsk agreement," Pushilin tweeted Friday.

Pushilin told reporters that. after the U.S.-Ukrainian exercises end, the equipment would remain in the country, Russian news agency Sputnik reported.

More than 6,000 people have lost their lives in the conflict between Ukrainian forces and pro-Russian separatists since April 2014, according to the United Nations.