US President Joe Biden has made a surprise visit to Ukraine early Monday — his first trip to the country since Russia’s invasion began nearly one year ago. Biden's trip is a show of support for Kyiv that comes at a critical moment in the conflict, as Russia prepares for an expected spring offensive.

The US President has said he visited Kyiv to reaffirm the United States’ “unwavering” support for Ukraine, announcing new military aid and a fresh swath of sanctions on the historic trip.

“As the world prepares to mark the one-year anniversary of Russia’s brutal invasion of Ukraine, I am in Kyiv today to meet with President Volodymyr Zelensky and reaffirm our unwavering and unflagging commitment to Ukraine’s democracy, sovereignty, and territorial integrity,” Biden said in a statement released by the White House.

“When Putin launched his invasion nearly one year ago, he thought Ukraine was weak and the West was divided. He thought he could outlast us. But he was dead wrong,” Biden said.

The President confirmed another donation of US military equipment, and said that later this week his government “would announce additional sanctions against elites and companies that are trying to evade or backfill Russia’s war machine.”

Biden is set to visit Poland later this week as he marks the anniversary of Russia’s invasion.

“I thought it was critical that there not be any doubt, none whatsoever, about US support for Ukraine in the war,” the US President said. “The Ukrainian people have stepped up in a way that few people ever have in the past.”

Biden emphasized there was broad, bipartisan support in Washington for the Ukrainian cause, even as some Republicans balk at providing further assistance.

“For all the disagreement we have in our Congress on some issues, there is significant agreement on support for Ukraine,” he said. “It’s not just about freedom in Ukraine … It’s about freedom of democracy at large,” he said.

Biden arrived in Kyiv at 8 a.m. local time (1:00 a.m. ET), according to reporters traveling with him inside Ukraine.

“It’s good to be back in Kyiv,” Biden said when he arrived. He was greeted by the US Ambassador to Ukraine Bridget Brink.

Biden’s motorcade arrived to the Mariinsky Palace just after 8:30 a.m. local time (1:30 a.m.ET). He was greeted at the entrance by Zelensky and his wife, Olena Zelenska.

“Thank you for coming,” Zelensky said shaking Biden’s hand. “More importantly, how are the children?” Biden asked, while adding: “It’s amazing to see you.”

Asked about the significance of being in Kyiv, Biden noted it was his eighth visit to the city. “Each time more significant,” Biden said.

He added that the purpose of his visit was to convey to Zelensky that the US is “here to stay.” “We’re not leaving,” Biden said.

CNN’s Chief International Correspondent Clarissa Ward described what she saw as US President Ukrainian counterpart in Kyiv earlier on Monday.

The pair arrived outside the city’s St. Michael’s Church, Ward told CNN’s Max Foster and Bianca Nobilo, entering the building from behind before leaving about five minutes later just before air sirens began to wail.

The two leaders then walked out of the church together, following two soldiers who were carrying wreaths to a wall of the fallen, commemorating those who have lost their lives in combat.

Ward went on to say the two leaders stayed there for a moment to pay their respects before embracing each other, showing the “rapport” the leaders have, she said.

President Biden’s trip to Kyiv on Monday was shrouded in secrecy, a reflection of the steep security concerns of visiting an active war zone.

Air Force One departed Joint Base Andrews under cover of darkness at 4:15 a.m. ET on Sunday. Reporters aboard the plane were not allowed to carry their devices with them.

Biden’s public schedule didn’t reflect the trip, and White House officials repeatedly said last week that a visit to Ukraine was not in the works.

On Saturday evening, before he departed, Biden went out to dinner with his wife in Washington. He wasn’t seen in public again until arriving in Kyiv on Monday morning.