The Ukrainian leader made the comments at a nuclear plant on his way to the Munich Security Conference, a day after U.S. President Donald Trump spoke to Russian leader Vladimir Putin Zelenskiy and announced the start of negotiations.

"We, as an independent country, simply will not be able to accept any agreements without us," Zelenskiy told reporters.

The Putin call and remarks by Trump's defence secretary, who said Kyiv cannot join NATO or that a return to Ukraine's pre-2014 borders is unrealistic, have caused alarm in Europe that the White House could seek to make a deal with Russia without them.

"Today it's important that everything does not go according to Putin's plan, in which he wants to do everything to make his negotiations bilateral (with the U.S.)," Zelenskiy said.

He said it was important for the United States and Ukraine to draw up a plan to end the war before talking to the Russian side.

He has been pushing to meet Trump before Trump meets Putin, although the U.S. president said on Wednesday that he was expecting to meet Putin in the future, probably in Saudi Arabia.

Ukraine has said it is working on a Zelenskiy-Trump meeting, but nothing firm has been announced so far.

Zelenskiy said he did not discuss the matter of NATO membership during his phone call with Trump, though he said he knew that the United States was against the idea.

He also tried to play down the significance of Trump calling Putin before him on Wednesday, saying it did not look like a marker of Washington's real priorities but adding that it was nonetheless "unpleasant".

As the third anniversary of Russia's invasion nears, Moscow controls a fifth of Ukraine and has been slowly advancing in the east for months, while Kyiv's smaller army grapples with manpower shortages and tries to hold a chunk of territory in western Russia.