Just days after hosting a summit in Warsaw on stability in the Middle East, U.S. Ambassador Georgette Mosbacher has called on Israel’s acting foreign minister to apologize to Poland.

Israel Katz, the minister, had claimed Sunday — the day he assumed the new cabinet position — that Poles had collaborated with Nazis during World War II and quoted former Israeli prime minister Yitzhak Shamir by saying that Poles “sucked anti-Semitism with their mothers’ milk.” Mosbacher, Washington’s envoy to Warsaw, said Wednesday that strong U.S. allies such as Israel and Poland “shouldn’t be using that kind of rhetoric. We are too important to each other not to work these things out.”

That the U.S. ambassador is trying to get the two close Washington allies to work through a diplomatic row is somewhat of a reversal of where things were last week — when the United States was convening friends for a summit over common interests.

Piotr Wilczek, the Polish ambassador to Washington, noted Mosbacher’s words. “We appreciate the US engagement, including that of some of the key Jewish American organizations,” he wrote in a statement to WorldViews, “particularly since good bilateral relations between Poland and Israel are also critical to the United States.”

For the Trump administration, the summit in Warsaw — which was originally supposed to be on Iran but was expanded thematically to attract attendees from more countries — was designed to bring countries together for a discussion of security issues in the Middle East. For Poland, it was an opportunity to play a prominent role on the international stage.

And for Israeli Prime Minister Benjamin Netanyahu, the summit “was useful, coming so close to the election in Israel and showing that Arab leaders are willing to be in the same room as him,” said Barbara Slavin, director of the Future of Iran Initiative at the Atlantic Council. All three had slightly different goals for the summit, but all could work together to achieve them.

But that was last week.

On his return from the summit, Netanyahu was quoted as saying that “the Poles” collaborated with Nazis during World War II (the Jerusalem Post, which quoted him, has since issued a correction to remove the definite article “the”). Katz then made matters worse with his own remarks.

Even Netanyahu has said that Katz’s comments were unfortunate, according to Czech Prime Minister Andrej Babis, who had a bilateral meeting with Netanyahu after Poland pulled out of a planned summit involving Israel and the Visegrad Four countries (the other two being Hungary and Slovakia).

“They were going to have a dog-and-pony show in Jerusalem with these rather conservative Central European countries,” Slavin said. “And now they’ve lost that.”

The United States, meanwhile, lost whatever momentum the Warsaw summit might have produced had it not been immediately followed by a diplomatic crisis between two close U.S. allies.

Last year, when Poland introduced a law that called for prison sentences of up to three years for those who accused Poles of committing crimes against Jews during World War II, the United States came down hard on Poland, reportedly barring its leaders from the White House.

But Mosbacher’s call for an apology, which came a day after she tweeted critically about Katz’s comments, made quite clear how the U.S. envoy, if not the whole Trump administration, felt about the issue.

“It put the U.S. in a difficult position, and certainly the ambassador in a difficult position,” Slavin said. “The Poles had just done us this huge favor” by hosting the Middle East summit.

The Polish Embassy in Washington, for its part, tried to separate the Warsaw summit from the diplomatic row.

“Together with our American counterparts we invited countries from the region and beyond and we provided a platform for all of these actors who otherwise don’t share a universal assessment of the situation in the Middle East. More often than not, they even don’t talk with one another,” Wilczek wrote.

"Our bilateral relations with Israel need to be viewed through a lens that is separate from the Warsaw Summit, which served as a multilateral gathering co-hosted by Poland and the USA and whose objectives will continue to be a work in progress, one that we intend to remain committed to,” he continued.

Still, he noted that Mosbacher had “called on Israel to apologize.”

Read more: