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The US intends to provide Ukraine with $500 million in "direct budgetary aid", President Joe Biden told Ukrainian President Volodymr Zelenskyy on Tuesday.
The additional aid is the latest round of assistance the US has provided to Kyiv as Russia's war against Ukraine drags on.
The US provided $800m in aid to Ukraine earlier this month that included Stinger anti-aircraft systems, Javelin missiles and drones.
In the hour-long phone call, Mr Biden and Mr Zelenskyy discussed America's ongoing efforts to supply Ukraine with military, economic and humanitarian assistance, the White House said in a readout of the call.
"The leaders discussed... continued efforts by the United States with allies and partners to identify additional capabilities to help the Ukrainian military defend its country," the White House said.
In a tweet, Mr Zelenskyy said he informed Mr Biden on the latest negotiation and war developments.
"Shared assessment of the situation on the battlefield and at the negotiating table. Talked about specific defensive support, a new package of enhanced sanctions, macro-financial and humanitarian aid," Mr Zelenskyy said on Twitter.
On Tuesday, peace talks between Ukraine and Russia appeared to have made their "most meaningful progress" since the invasion began, Turkey's foreign minister said, after Moscow vowed it would curtail its military operations near Kyiv.
Moscow's promise was met with scepticism in the West, as Mr Biden told reporters he would not "read anything into it until I see what their actions are."
The Pentagon added that the movement of Russian forces was more of a repositioning than a withdrawal, adding that any redeployment of troops from the Ukrainian capital indicates a significant setback for Moscow.
A US official, speaking on the condition of anonymity, said Russian President Vladimir Putin is being misinformed by his advisers about his forces' struggles, AP reported.
In Washington, lawmakers on Capitol Hill continue to press ahead with a Russian sanctions package. After it was overwhelmingly approved by the House, the legislation designed to revoke Russia's preferred trade status has been stuck in the Senate for weeks.
Some progress appeared to be made on Wednesday after language of the bill was changed to satisfy Rand Paul, a Republican senator, whose opposition has forced the bill to stall.
Members of both chambers are expected to be briefed on developments in Ukraine later in the afternoon.
