KYIV, March 24 (Reuters) - Ukrainian President Volodymyr Zelenskyy on Thursday (Mar 23) urged Europe to increase and speed up supplies of modern weaponry and impose tougher sanctions on Russia, saying otherwise the war could drag on for years.

In a long and sharply worded video address to EU leaders, delivered from a train, Zelenskyy said it was up to the 27-nation bloc to take action to contain Russia more than a year into its invasion of Ukraine.

Although Ukrainian officials have repeatedly urged partners to step up supplies of weapons, Zelensyy's comments represented an unusually open display of frustration.

"If Europe waits, the evil may have time to regroup and prepare for years of war. It is in your power to prevent this," he said in an address to EU leaders, who held talks with UN chief Antonio Guterres.

It was the EU, he said, that had delayed decisions on providing long-range weapons and modern fighter aircraft and in moving forward with talks on granting Ukraine EU membership.

"Dear colleagues, do you not feel that we have had fewer successes than delays in our joint actions? Unfortunately, that is the case. And the Kremlin sees that," he said.

"We cannot keep delaying the transfer of weapons to our soldiers ... we need modern aircraft. We talked about this. Is there truly any rational motivation in delays concerning modern aircraft?"

Zelenskyy thanked Poland and Slovakia - now NATO members and formerly part of the Warsaw Pact - for agreeing to supply Soviet-built MiG aircraft that Ukrainian pilots can fly without additional training.

Western allies have expressed severe reservations about sending up-to-date western fighters to Ukraine.

Zelenskyy also complained that the EU appeared to be in no hurry to impose more sanctions against Russia.