President Biden and Ukrainian President Volodymyr Zelensky spoke by phone Monday ahead of the commander-in-chief’s summit with Russian President Vladimir Putin next week, National Security Adviser Jake Sullivan revealed — despite pleas from the Ukrainian leader for a face-to-face meeting.

Sullivan made the announcement while speaking to reporters at a White House press briefing.

“President Biden was able to tell President Zelensky that he will stand up firmly for Ukraine’s sovereignty, territorial integrity and and its aspirations as we go forward. And he also told President Zelensky that he looks forward to welcoming him to the White House this summer, after he returns from Europe,” Sullivan said.

However, Zelensky, in an hour-long interview with Axios published Sunday, said it is imperative to conduct an in-person meeting ahead of the Putin summit, adding he would make himself available to meet with the US president at a moment’s notice.

“I believe that it is up to them [to brief Ukraine],” he began, “However, I do think that it would be a big mistake [not to],” Zelensky told Axios ahead of the US-Russia summit.

“We understand the steps they are taking,” the Ukrainian president continued, referring to Russia’s military aggression and “the numbers of personnel amassed along the contact line and on the temporarily occupied territories.”

Zelensky then discussed his effort to lock down a face-to-face meeting with the US president before his Putin meeting, which he’s thus far had no luck securing.

“That is why I consider such consultations to be important. I believe such consultations should happen face-to-face, because many things just cannot be discussed over the phone. I understand that due to the US president’s pre-existing plans and his tight schedule they might well not happen, but that choice will be only his to make.”

“As the guarantor of the constitution of Ukraine, I myself am ready to defend Ukraine at any moment and at any moment and at any spot on the planet. I am ready to meet with him and discuss all those details before his meeting. However, we’ll see how it ends up going. I am sure that some sort of contact between us, in that form or another, is quite possible.”

The White House did not immediately respond to The Post’s request for comment on the possibility of a Zelensky meeting before next Wednesday. Nor did the State Department.

The Ukrainian president also maintained his staunch opposition to Nord Stream 2, the controversial pipeline from Russia to Germany that would circumvent and isolate his country’s capital of Kyiv. Biden decided to waive sanctions against the Russian-owned company behind the project last month, arguing “it’s almost completely finished.”

Germany, a critical US ally, is also a major proponent the pipeline’s construction being completed.

“It’s almost completely finished, number one. The idea that anything that — and it’s not like I can allow Germany to do something they’re not,” Biden said when explaining his decision.

While he claimed he had been opposed to Nord Stream 2 from the beginning, it was “almost completed by the time I took office.”

Reached for comment by Axios, the White House said, “The administration is committed to continuing to consult with Ukraine as we press Germany to address the risks Nord Stream 2 poses to Ukraine and European energy security. We also welcome Ukraine’s direct engagement with the German government about their concerns.”

“When President Biden meets with President Putin in Geneva, he will stand up for Ukraine’s sovereignty and territorial integrity, as he has done in both of his earlier calls to President Putin.”

Putin presided over the annexation of Crimea in 2014 without Ukraine’s consent in a rare present-day boundary change by force.

Russian troop deployments are often murky, but Putin’s government is believed to have deployed troops to Crimea to facilitate the 2014 annexation and to have secretly supported a pair of breakaway provinces in eastern Ukraine’s Donbas region.

Moscow has continued to flex its military muscle in Ukraine and in the Black Sea in recent months — along with its warning to the US to back off, which caused Biden to turn two US warships around in April that were headed there.

Biden declared a national emergency that month, slapping sanctions on more than three dozen people in Russia and expelling 10 diplomats.

Putin subsequently closed off the Kerch Strait to foreign warships until next fall.

On Monday, Putin signed a law officially ending the country’s involvement in the Open Skies Treaty, an international arms control pact that allows nations to conduct unarmed surveillance flights over each other’s territories.

Then-President Trump withdrew from the agreement last year, after a six-month review that found multiple instances of Russia refusing to comply with the agreement.

Once in office, Biden said he would not re-enter the pact.