Washington DC - President Donald Trump is to meet Ukrainian President Volodymyr Zelensky on the sidelines of the NATO summit on Wednesday afternoon, as efforts drag on to end Russia's war against Ukraine, a spokesperson said on Sunday.

The two-day summit of the NATO alliance begins on Tuesday in the Turkish capital Ankara.

Neither Russia nor Ukraine is making any significant military progress, as their mutual attacks penetrate deep into each other's territory, a senior US official stressed to journalists. 

"So the president feels a real sense of urgency to try to bring this to a stop," the official said.

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The US is confident that progress could be made when Trump and Zelensky meet.

Trump would also get in touch with Russian President Vladimir Putin, the official said.

The US has been mediating between Russia and Ukraine in the war for some time. But the efforts have recently taken a back seat, given the US-Israeli war against Iran.

At the NATO summit, Ukraine is also to receive a new pledge of military aid worth billions of euros. Representatives of the alliance's 32 member states agreed on this in Brussels a few days before the top-level meeting during final deliberations on the planned summit declaration, as dpa learned.

According to the government spokesperson, Trump also wants to meet Turkish President Recep Tayyip Erdoğan for bilateral talks on Tuesday evening after arriving in Ankara.

In addition to the meeting with Zelensky on Wednesday, Trump also wants to hold talks with Syria's transitional president, Ahmed al-Sharaa. Other bilateral meetings were initially not made public. 

Trump is scheduled to leave Ankara for Washington on Wednesday evening.