German Foreign Minister Annalena Baerbock has sharply criticised Pope Francis's call for Ukraine to negotiate with Moscow, saying she didn't "understand" his stance.

The pope sparked a furore at the weekend after saying in an interview on Swiss television that one should "have the courage to raise the white flag and negotiate", two years into Moscow's invasion of Ukraine.

"I don't understand it," Baerbock said in a talk show on public broadcaster ARD late Sunday.

"I think some things you can only understand if you see them for yourself," added Baerbock, who has travelled to Kyiv several times since the start of the war.

When talking to children in Ukraine who are suffering because of the war, she said, "I ask myself: Where is the pope? The pope must know about these things."

Baerbock said if Ukraine and its allies "don't show strength now, there will be no peace".

"We must stand by Ukraine and do everything we can to ensure that it can defend itself," she added.

A spokesman for Chancellor Olaf Scholz was also asked about the pontiff's remarks in a regular press conference on Monday.

"As you can imagine, the chancellor does not share the pope's opinion on this issue," spokesman Steffen Hebestreit said, adding that Ukraine was "defending itself against an aggressor".

Germany is the second-biggest supplier of military aid to Ukraine, after the United States.

Berlin is facing growing pressure to deliver long-range Taurus cruise missiles to Ukraine but Scholz has so far rebuffed those calls, citing concerns about potentially escalating the conflict.

Kyiv on Sunday responded angrily to the pope's "white flag" appeal, with Foreign Minister Dmytro Kuleba saying his country would "never" surrender.

Ukrainian President Volodymyr Zelensky also hit back at the comments.

Ukrainians of all faiths stood up to defend their country when Russia invaded, he said in his evening address on Sunday.

"Christians, Muslims, Jews -- everyone... They support us with prayer, conversation, and deeds.

"This is what the church is -- with people. And not two and a half thousand kilometres away, somewhere to mediate virtually between someone who wants to live and someone who wants to destroy you."