The speaker of the U.S. House of Representatives, Nancy Pelosi, has made a surprise visit to Kyiv to meet with Ukrainian President Volodymyr Zelenskiy and other officials.

Zelenskiy posted videos from the unannounced April 30 visit online on May 1.

“We believe that we are visiting you to say thank you for your fight for freedom,” Pelosi told Zelenskiy. “We are on a frontier of freedom, and your fight is for everyone. Our commitment is to be there for you until the fight is done.”

Pelosi arrived in the Ukrainian capital with a delegation that included House members Jason Crow (Democrat-Colorado), Jim McGovern (Democrat-Massachusetts), and Adam Shiff (Democrat-California). The trip had not been previously announced and comes when the United States and other countries are ramping up military aid and other support for Ukraine.

Pelosi said the delegation “delivered the message that additional American support is on the way.”

U.S. President Joe Biden last week asked Congress for a $33 billion aid package for Ukraine.

Zelenskiy posted on Twitter: “The U.S. is leading strong support for Ukraine in its fight against Russian aggression.”

Pelosi said the delegation would visit Poland for talks with President Andrzej Duda and other officials. Poland has taken in more than 3 million refugees from Ukraine since the war began.

Meanwhile, Ukrainian Foreign Minister Dmytro Kuleba was in Beijing on May 1 to ask China to provide security guarantees as part of any future peace agreement between Ukraine and Russia.

“Ukraine is currently studying the possibility of acquiring security guarantees from permanent members of the UN Security Council, including China and other major powers,” Kuleba told Chinese media.

The United Nations was continuing efforts to arrange the evacuation of civilians from the embattled Ukrainian Azov Sea port of Mariupol as intense fighting and shelling continues across Ukraine’s south and east.

UN spokesman Saviano Abreu told journalists in Ukraine’s Zaporizhzhya that negotiations on evacuating civilians from Mariupol were proceeding in Moscow and Kyiv, but he could not report progress “because of the complexity and fluidity of the operation.”

The UN believes about 1,000 civilians are living under the Azovstal steelworks in the city, the only part of Mariupol that is not under Russian occupation. There are believed to be about 100,000 civilians in the city, which has been the scene of intense fighting since the Russian invasion on February 24.