President Biden spoke by phone with Ukrainian President Volodymyr Zelensky Tuesday as Ukrainian forces continued to drive back Russian invaders on two fronts.

The call took place days after Russian tyrant Vladimir Putin claimed to annex four regions of Ukraine — some 18% of the country — and vowed to back up his claim with nuclear weapons if necessary.

Biden signed a bill Friday authorizing another $12 billion in US aid for the Kyiv government while insisting the US will “never” accept Russia’s annexation attempt.

Biden, joined on Tuesday’s call by Vice President Kamala Harris, “underscore[d] that the United States will never recognize Russia’s purported annexation of Ukrainian territory,” the White House said in a statement after he phoned Zelensky.

The president also “pledged to continue supporting Ukraine as it defends itself from Russian aggression for as long as it takes, including the provision today of a new $625 million security assistance package that includes additional weapons and equipment, including HIMARS, artillery systems and ammunition, and armored vehicles.”

Biden additionally “affirmed the continued readiness of the United States to impose severe costs on any individual, entity, or country that provides support to Russia’s purported annexation,” the White House said.

“[Biden] welcomed the success of the agreement that has allowed the safe export of Ukrainian grain to global markets and the need to ensure that continues,” the readout added. “In addition, President Biden noted the ongoing efforts of the United States to rally the world behind Ukraine’s efforts to defend its freedom and democracy, as enshrined in the United Nations Charter.”

Meanwhile, Zelensky announced Tuesday he had ruled out negotiations with Russia as long as Putin held power after the annexation announcement was rubber-stamped by Moscow’s parliament, the Duma.

The Kremlin replied by saying that it will wait for Ukraine to agree to sit down for talks and that it may not happen until a new Ukrainian president takes office.

“We will wait for the incumbent president to change his position or wait for a future Ukrainian president who would revise his stand in the interests of the Ukrainian people,” Kremlin spokesman Dmitry Peskov said.

Biden’s predecessor, former President Donald Trump, was impeached in 2019 for pressuring Zelensky to investigate first son Hunter Biden’s $1 million-per-year job at Ukrainian gas company Burisma while Joe Biden, then vice president led the Obama administration’s Ukraine policy.

Russia annexed the Crimean peninsula from Ukraine in 2014 following a referendum that lacked international credibility and had supported pro-Russia rebels in Ukraine’s Donetsk and Luhansk regions in their long-running conflict with Kyiv before Moscow openly invaded the country on Feb. 24.