US ambassador to Warsaw called on Israel to apologize to Poland in a row between the two countries over the Holocaust, after Israel’s acting foreign minister said “many Poles” had collaborated with the Nazis, Reuters reported.

The row, initially sparked by media reports suggesting Prime Minister Benjamin Netanyahu accused Poles of complicity in the Holocaust, deepened on Monday after the comment by his minister Israel Katz, who also labeled Poles anti-Semites.Katz’s words led Poland to pull out of a planned summit of central European states in Israel.

US ambassador Georgette Mosbacher, asked if Katz should apologize, said the comment “warrants an apology”. Mosbacher said she felt two strong allies like Israel and Poland “shouldn’t be using that kind of rhetoric. We are too important to each other not to work these things out.”