U.S. senators addressed a letter to President Barack Obama, calling on him to impose new sanctions against Russia, specifically the energy, finance and defense sectors of Russia’s economy.

“We urge you to implement your power in order to impose broader sanctions against Russia’s defense sector immediately, including state company Rosoboronexport. Russians must stop providing weapons, equipment and training to separatists in eastern Ukraine. We also urge you to consider further sanctions targeting energy, finance and other sectors of Russian economy,” the letter said, according to RIA Novosti.

Senate Committee on Foreign Relations chairman Robert Menendez, Select Committee on Intelligence head Dianne Feinstein and Armed Services Committee chairman Carl Levin signed the document.

Senators also asked Obama to add the self-proclaimed Donetsk People’s Republic to U.S. terrorism blacklist.

“We call to consider the possibility of considering Donetsk People’s Republic a foreign terrorist organization. An increasing evidence of human rights violations in the east of Ukraine, including cases of kidnapping and torture indicate that their actions threaten lives of innocent Ukrainians, not to mention those poor people who just travelled in the Ukrainian airspace,” the letter said.