BRUSSELS (Reuters) -Training Ukrainian pilots on Western F-16 fighter jets does not make NATO a party to the conflict, its chief Jens Stoltenberg said on Tuesday, as allies pledged to speed up preparations to start lessons.

Stoltenberg said Ukraine had the right to defend itself.

"We help Ukraine to uphold that right," he told reporters in Brussels. "That doesn't make NATO and NATO allies a party to the conflict."

On Monday, senior Russian diplomats on Monday said the transfer of F-16 jets to Ukraine would raise the question of NATO's role in the conflict.

U.S. President Joe Biden on Friday endorsed training programs for Ukrainian pilots on F-16s. Ukrainian President Volodymyr Zelenskiy assured Biden that the planes would not be used to cross into Russian territory.

"This is an important step that apparently will enable us to then deliver fighter jets at some stage," said Stoltenberg, who described the move as "a very clear signal that we are there for the long term and that Russia cannot wait us out".

A fighter jet coalition of nations was meanwhile hammering out the concrete timeline for starting the training.

"We will speed up now that we have the green light," Dutch Defence Minister Kajsa Ollongren told reporters on the sidelines of a meeting with her EU counterparts in Brussels.

She said the training were a coordinated effort by Belgium, Denmark, Britain, the Netherlands and other allies, and that more countries could join.

Germany said it was looking into ways to support the fighter jet coalition.

"We are looking into the few options that we may theoretically have," Defence Minister Boris Pistorius said.

"But it won't be significant as we simply don't have F-16 fighter jets on our own and are unlikely to be able to help a lot in the pilot training".

(Reporting by Sabine Siebold and Andrew Gray; editing by John Stonestreet)