WASHINGTON, Jan 17, 2024 (BSS/AFP) - US President Joe Biden has invited Congressional leaders for talks Wednesday on continuing "critical" aid for Ukraine, the White House said, as concerns mount over Western support against Russia.

Washington's military assistance for Ukraine has dried up, with Republicans blocking Democrat Biden's request for $60 billion in aid for Ukraine unless he tightens US immigration laws.

The money for Ukraine is also caught in a bitter partisan political divide as Congress tries to reach a deal to avoid a fresh US government shutdown on Friday.

Biden will host US House of Representatives and Senate leaders "at the White House to discuss the critical importance of his national security supplemental request," Press Secretary Karine Jean-Pierre told reporters.

Jean-Pierre said Biden would underscore "how important it is to get moving on that".

The talks could signal a step forward in the negotiations on US funding for Ukraine, as Biden has for weeks declined to get involved in meetings with Republicans.

Biden also spoke to German Chancellor Olaf Scholz on Tuesday and they "coordinated on their countries'' ongoing steadfast support to Ukraine in the face of Russia's war of aggression," the White House said.

Concerns have mounted over the fate of Ukraine as the United States -- Kyiv's main backer since Russia's February 2022 invasion -- has been unable to agree on fresh aid since last September.

Ukrainian President Volodymyr Zelensky, who visited Washington in December in a failed bid to convince Congress to change its mind, met key US officials at the Davos forum this week.

Zelensky, US Secretary of State Antony Blinken and Biden's National Security Advisor Jake Sullivan discussed aid, developments on the battlefield and Zelensky's ideas for a "peace formula," the White House said.

Russian President Vladimir Putin said Tuesday that Moscow's forces had the upper hand and Ukraine risked an "irreparable" blow if it continued. Moscow has rejected any peace plan that does not let it keep conquered territory.