"We failed on many points," the president told German public broadcaster ZDF. "It is true that we should have taken the warnings of our eastern European partners more seriously, particularly regarding the time after 2014."
One of Steinmeier's most prominent critics of his ties with Russia has been the Ukrainian Ambassador to Germany Andriy Melnyk. He called Steinmeier's comments a "first step" in an interview with Germany's Deutschlandfunk radio.
Ukraine's Foreign Minister Dmytro Kuleba also responded to the comments, saying he welcomed Steinmeier's "honest words."
"I call on Germany and other EU states to correct them now with swift and resolute actions," Kuleba wrote on Twitter. "Weapons and sanctions. We don't have time anymore."
Ambassador Melnyk also urged action, not just words.
"I would rather, as would many of my people, that the German president wouldn't just show regret, but would call on the government to take the lessons from the massacre at Bucha, from the other atrocities that are being witnessed day and night in Ukraine," Melnyk said.
Nord Stream 2 was a 'mistake'
Melnyk had previously implied that Steinmeier held the similar view to Russian President Vladimir Putin that "there is no Ukrainian people," according to an interview with the German newspaper Tagesspiegel.
The ambassador also claimed that the German president had too many vested interests in Russia, a criticism that was rejected by government spokesperson Wolfgang Büchner.
Steinmeier served two non-consecutive stints as foreign minister under Chancellor Angela Merkel, a position he held during Russia's 2014 invasion of Ukraine — which ended with Moscow taking de facto control of the Ukrainian peninsula of Crimea, and backing a continuous war in the eastern Donbas region.
During Steinmeier's tenure at the Foreign Ministry, Germany bolstered its energy ties with Moscow, especially when it came to gas imports.
Germany draws criticism from Poland, Ukraine
Germany's decision to carry on with the construction of the Nord Stream 2 pipeline in spite of Russia's actions drew international criticism and particular ire from Washington.