WASHINGTON, April 24 -- U.S. State Secretary John Kerry on Thursday accused Russia of inaction in helping ease the tense situation in eastern Ukraine, while his Russian counterpart Sergei Lavrov urged Washington to press Kiev to refrain from using force against pro-Russia protesters.

The top American envoy charged Russia of refusing to take "a single concrete step in the right direction" for the past seven days, since the the United States, the European Union, Russia and Ukraine agreed in Geneva April 17 to takes steps to de-escalate tension in eastern Ukraine, according to a statement released to the press.

He warned that "window to change course" was closing for Russia and the the United States was "ready to act" by imposing more sanctions on Moscow.

Meanwhile, Russian Foreign Minister Lavrov said Russia is against any violence, and the use of army against people, or backing radical nationalists, is an absolutely unacceptable form of violence.

Lavrov urged the United States to use its influence to make the Ukrainian authorities fulfill their commitment of the Geneva agreement on Ukraine.

The main condition to solve the ongoing crisis in Ukraine was to "stop illegal actions of current Kiev authorities, which should understand their responsibility for everything agreed upon in Geneva on Feb. 21 and April 17," Lavrov said.

Lavrov also accused the United States and the EU of attempting to stage "another Color Revolution" in Ukraine for "an unconstitutional change of regime."

The Obama administration has ruled out a military solution to the Ukrainian crisis, but it ratchet up sanctions on Russia, targeting entities and key sectors including energy, banking, mining and defense.

The Ukrainian government resumed its "anti-terror" operations on Wednesday in several states in eastern Ukraine, where pro-Russia militants are refusing to leave government buildings under their occupation in a number of cities.

At least five militants were killed on Thursday outside the city of Slavyansk, Ukrainian Interior Ministry said in a statement.

Russia also urged the the United States to press the Ukrainian authorities to halt the operations, and begun military drills near the border with Ukraine in response.