US Secretary of State Marco Rubio spoke by phone with Russian Foreign Minister Sergei Lavrov at the request of the Russian side, the US State Department press service reported.

"Secretary of State Marco Rubio spoke with Russian Foreign Minister Sergey Lavrov on Sunday at Russia's request. Secretary Rubio reiterated President Trump's call for continued direct negotiations between Russia and Ukraine to achieve a lasting peace," said US State Department spokeswoman Tammy Bruce.

Combined attacks by the Russian Federation are forcing Ukraine to make difficult decisions about which areas to protect with only a limited number of Patriot air defense systems, according to analysts at the Washington-based Institute for War Studies (ISW).

They recalled that on the night of May 31 to June 1, the Russian military carried out the largest combined drone and missile attack to date. The Russians launched three Iskander-M/KN-23 ballistic missiles,

Ukraine is ready to take"big steps" in a second round of talks with Russian officials scheduled for Monday in Istanbul to make progress towards peace, a source in the Kyiv delegation told AFP.

"The Ukrainian delegation arrived in Istanbul with a clear agenda and ready to take big steps towards peace," the source claimed, adding that Ukraine hopes that the Russian side"will not repeat the same previous ultimatums."

The day before the talks on Monday, Ukrainian security services conducted a special operation in the Russian hinterland, and Russian strategic bombers were set ablaze, Ukrinform was told by sources in the agency.