Russian President Vladimir Putin told U.S. President Donald Trump during a phone call Tuesday that Moscow has no aggressive intentions toward Europe, the Kremlin said, as European officials raise concerns over suspected Russian sabotage operations across the continent.

Ukrainian President Volodymyr Zelenskyy said meanwhile that U.S. envoys who visited Kyiv presented some "very good, worthwhile ideas" for ending Russia's 4 1/2-year-old war, adding that he hopes to meet with Trump within two weeks.

But Russia remains determined to accomplish its military goals and it believes it is close to winning, Kremlin spokesman Dmitry Peskov said. Ukrainian and Western observers believe that Moscow has been unable to make any significant progress on the front line.

The war could yet drag on for years as Russia reconstitutes its forces and its defense industry, said U.S. Undersecretary of Defense Elbridge Colby.

"We must be prepared for a protracted conflict and for Ukraine's requirements to persist in the months and years ahead," Colby told an online meeting of countries helping Ukraine.