Ukrainian President Volodymyr Zelenskyy said Tuesday that U.S. peace negotiators are focused on the Iran conflict and have "no time for Ukraine," according to an interview.

Zelenskyy told German public broadcaster ZDF that Steve Witkoff and Jared Kushner, who have helped broker talks with Moscow on ending Russia's war on Ukraine, were "constantly in talks with Iran" at the moment.

Describing the pair as "pragmatic", Zelenskyy said they were trying to "get more attention from Putin in order to end the war."

But "if the United States does not put pressure on Putin (...) and only engages in a gentle dialogue with the Russians, then they will no longer be afraid", he said.

U.S.-led talks to end Europe's deadliest conflict since World War II have stalled since the Iran war erupted in late March, and Russian and Ukrainian negotiators have not met since February in Geneva.

Zelenskyy said that the issue of deliveries of U.S. arms to Ukraine has become "a big problem."

"If the war goes on, there will be less arms for Ukraine. It's critical, especially in materials for air defences," he said.

Zelenskyy later told a press conference during a visit to Norway that this was especially a problem for PAC-3 interceptor missiles, as well as the PAC-2 missile.

He said these were primarily bought through the PURL programme, which was launched last year and allows Ukraine to receive U.S. equipment financed by European countries.

"At the very beginning of... (the) war in the Middle East we understood that we can have challenges," Zelenskyy said.

Zelenskyy said deliveries came "slowly", noting it was a "very difficult position for us."

Zelenskyy made the comment alongside Norwegian Prime Minister Jonas Gahr Store, with the two leaders announcing they had signed "a joint declaration on enhanced defence and security cooperation."

The Norwegian government said in a statement that the countries wished to "facilitate closer cooperation between the Norwegian and Ukrainian defence industries" and that "Ukrainian drones will now be manufactured in Norway."

Earlier on Tuesday, Zelenskyy led a government delegation to Berlin, where they met Chancellor Friedrich Merz and key ministers to discuss Ukraine's war against Russia, now in its fifth year.

The two countries also announced a strategic partnership centred on defense.