US will not return nuclear weapons to Ukraine — official

The United States is not considering returning to Ukraine the nuclear weapons it gave up after the Soviet Union collapsed, White House national security adviser Jake Sullivan has said.

Sullivan made his remarks when questioned on Sunday about a New York Times article last month that said some unidentified Western officials had suggested US President Joe Biden could give Ukraine the arms before he leaves office.

"That is not under consideration, no. What we are doing is surging various conventional capacities to Ukraine so that they can effectively defend themselves and take the fight to the Russians, not (giving them) nuclear capability," he told ABC.

Last week, Russia said the idea was "absolute insanity" and that preventing such a scenario was one of the reasons why Moscow sent troops into Ukraine.

Kiev inherited nuclear weapons from the Soviet Union after its 1991 collapse but gave them up under a 1994 agreement, the Budapest Memorandum, in return for security assurances from Russia, the United States and Britain.

'Strong position'

Meanwhile, Ukrainian President Volodymyr Zelenskyy said on Sunday that his country needed to be in a "strong position" before any talks with the Kremlin, calling for "steps forward with NATO" and a "good number" of long-distance weapons to defend itself.

"Only when we have all these items and we are strong, after that, we have to make the very important... agenda of meeting with one or another of the killers," the Ukrainian leader said, adding that the EU and NATO should be involved in any negotiations.

He made the comments after meeting the EU's new head of diplomacy Kaja Kallas and EU Council chief Antonio Costa, who visited Kiev as a show of support on their first day in office.

"An invitation for Ukraine to join NATO is a necessary thing for our survival," Zelenskyy said at a press conference with Costa.

Costa said the European Union would give Ukraine its "unwavering" support.

"We have stood with you since the very first day of this war of aggression, and you can count on us to continue to stand with you," he told Zelenskyy.

'The strongest security guarantee'

Zelenskyy also called on NATO to offer guaranteed protections to parts of Ukraine controlled by Kiev in order to "stop the hot stage of the war", and implied he would then be willing to wait to regain other territory seized by Russia.

"If we will have a frozen conflict without any strong position for Ukraine, Putin will come back in two, three or five years," Zelenskyy said.

Kallas told journalists on the journey into Ukraine that for Kiev "the strongest security guarantee is NATO membership".

But diplomats at NATO say there appears little prospect of the alliance granting Ukraine membership soon given opposition from a number of members cautious of getting dragged into war with Russia.

Zelenskyy insisted Kiev was not "delusional" about its prospects with NATO and admitted there was deep reluctance from US President Joe Biden, along with leaders in countries such as Hungary.