U.S. President Donald Trump on Tuesday said on social media that he believes Ukraine, with support from Europe and NATO, "is in a position to fight and WIN all of Ukraine back in its original form."

The remarks signaled a sharp shift in the White House's position on the Russia-Ukraine conflict since Trump has for months pressed Ukrainian President Volodymyr Zelensky to make concessions to reach a ceasefire deal with Russia, claiming Kiev "doesn't have the cards" in the negotiations.

"After getting to know and fully understand the Ukraine/Russia Military and Economic situation and, after seeing the Economic trouble it is causing Russia, I think Ukraine, with the support of the European Union, is in a position to fight and WIN all of Ukraine back in its original form," Trump wrote on Truth Social.

"With time, patience, and the financial support of Europe and, in particular, NATO, the original Borders from where this War started, is very much an option," Trump said.

"We will continue to supply weapons to NATO for NATO to do what they want with them," said the president.

When meeting with Zelensky on the sidelines of the United Nations General Assembly in New York City earlier on Tuesday, Trump told reporters that NATO countries should shoot down Russian jets that violate their airspace.

In a letter dated Saturday and addressed to the president of the UN Security Council, Estonia claimed that three Russian MiG-31 fighters entered up to 10 km inside Estonia's airspace and stayed for 12 minutes on Friday.

Russia's first deputy permanent representative to the United Nations, Dmitry Polyanskiy, denied that Russian jets had violated Estonian airspace and accused European states of Russophobia.

Geng Shuang, China's deputy permanent representative to the United Nations, said Monday that China urges the parties concerned to remain calm and exercise restraint, clarify facts and dispel doubts through dialogue and communication, avoid misunderstanding and misjudgment, and prevent the situation from expanding or escalating.