KYIV — The United States will not provide the F-16 fighter jets that Ukraine has sought in its battle against Russia, President Joe Biden said, as Russian forces claimed a series of gains on the battlefield.

Asked if the US would provide the jets, Biden told reporters at the White House on Monday: "No."

Ukraine planned to push for Western fourth-generation fighter jets, such as the F-16, after securing supplies of main battle tanks last week, an adviser to Ukraine's defense minister said on Friday.

"The next big hurdle will now be the fighter jets," Yuriy Sak, who advises Defense Minister Oleksiy Reznikov, told Reuters then.

But France and Poland appear to be willing to entertain any such request from Ukraine, with French President Emmanuel Macron telling reporters in The Hague on Monday that "by definition, nothing is excluded" when it comes to military assistance.

In Poland on Monday, Prime Minister Mateusz Morawiecki also did not rule out a possible supply of F-16s to neighboring Ukraine, in response to a question from a reporter before Biden spoke.

Lithuanian President Gitanas Nauseda said on Monday that NATO should stop drawing "red lines" and should supply Ukraine with whatever weapons it needed, including fighter jets and long-range missiles.

'Aggressive position'

Russia warned on Tuesday that calls by the president of Lithuania to supply Ukraine with fighter jets highlighted the "extremely aggressive position" of the Baltic states and Poland, and that "major European countries" should counterbalance their stance.

Kremlin spokesman Dmitry Peskov told reporters: "In general, we see an extremely aggressive position from representatives of the Baltic countries and Poland. They are apparently ready to do anything to provoke the growth of further confrontation, with little regard for the consequences."

Ukrainian President Volodymyr Zelensky has warned for weeks that Moscow aims to step up its assault after about two months of virtual stalemate along the front line that stretches across the south and east.

Ukraine won a huge boost last week when Germany and the US announced plans to provide heavy tanks, ending weeks of diplomatic deadlock on the issue.

While there was no sign of a broader new Russian offensive, the administrator of Russian-controlled parts of Donetsk, Denis Pushilin, said Russian troops had secured a foothold in Vuhledar, a coal-mining town whose ruins have been a Ukrainian bastion since the outset of the conflict.

Meanwhile, Russian Deputy Foreign Minister Sergei Ryabkov on Monday met with new US Ambassador to Russia Lynne Tracy, who presented copies of her credentials.

During the conversation with Tracy on the sharply worsened Russia-US relations, Ryabkov pointed out the counterproductiveness of Washington's confrontational policy, which is "fraught with serious negative consequences", the Russian Foreign Ministry said in a statement.

Taking office on Jan 9, Tracy is the first woman to occupy the post of US ambassador to Russia.

                                                                                                        Xinhua