The U.S. and Ukrainian forces started joint military exercises on Monday. Speaking at the inauguration ceremony, Ukrainian President Petro Poroshenko said that the military exercises were aimed at strengthening Kiev’s defenses against Russian-backed separatists. Russia has reacted strongly to the exercise, dubbed ‘Fearless Guardian-2015.’

Russia Rattled As US-Ukraine Start Joint Military Exercise

Russia warns of potential destabilization

Russia warned that the U.S.-Ukraine military training could potentially destabilize the region. Meanwhile, Petro Poroshenko said that Ukraine’s armed forces “needed to be rebuilt from scratch,” according to the Associated Press. Russia continues to deny any involvement in supporting separatists in Ukraine. However, Ukraine and Western powers have accused Moscow of providing arms to separatists.

The separatist insurgency in Ukraine has claimed more than 6,100 lives since last year. Last week, 300 U.S. Army paratroopers traveled to Ukraine to participate in the exercises that also involve 900 Ukrainian national guardsmen. Poroshenko said most of the participants from the Ukrainian side had “endured difficult trials on the front.”

Fights in the eastern Ukraine have subsided significantly since Russia and Ukraine signed a ceasefire agreement in February. But occasional clashes still occur between separatists and government forces. Now Russia says that the U.S. is violating the ceasefire agreement by stationing its forces in Ukraine. The ceasefire deal included provisions that all “armed formations” must be pulled out of Ukraine.

U.S. taking measures to counter Russian aggression

Besides training Ukrainian forces, the U.S. is providing assistance to counter Russia. Last month, the U.S. started delivering 230 Humvees to Ukraine. President Barack Obama is also providing Kiev $75 million in non-lethal aid. But the Congress has urged the Obama administration to supply lethal arms to Ukraine. NATO forces are also strengthening their presence in eastern Europe to counter any aggression from Russia.

Last week, Russian Defense Minister Sergei Shoigu said that the U.S. had forced Moscow to react on Ukraine. Shoigu accused the U.S. of seeking complete political and military dominance in the region without taking in account the interests of other countries.