Swedish Prime Minister Ulf Kristersson said on Wednesday the election of Donald Trump as US president could put Washington's commitment to Ukraine at risk.

Kristersson congratulated Trump on his victory in a post to X early Wednesday. He was looking forward "to working together and continuing the excellent US-Sweden relations as friends and allies", he wrote.

But hours later, Kristersson told a news conference that Trump's return to the Oval Office also carried risks, including "existential" ones for Sweden such as a potential US "reduced commitment to Ukraine".

"I'm not going to count on it," Kristersson told reporters.

"On the contrary, we take stock of the fact that the US is until now the single largest military aid donor to Ukraine.

"We don't take it for granted."

Added together, he noted, the Nordic and Baltic countries were the second-largest donor to the Ukrainian war effort.

Trump has cast doubt on continuing US military support for Kyiv, promising to cut a quick deal with Russian President Vladimir Putin to end the war.

Sweden ended two centuries of military non-alignment and applied for Nato membership in the wake of Russia's 2022 invasion of Ukraine -- becoming the US-led alliance's 32nd member in March of this year. (AFP)