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LONDON — Vice President Mike Pence on Thursday accused Iran of pursuing "another Holocaust" as he lashed out at some of America's closest allies for trying to undercut U.S. sanctions against Tehran.

“The Iranian regime openly advocates another Holocaust and seeks the means to achieve it,” Pence told delegates at a U.S.-organized Middle East conference in Poland on Thursday.

In an effort to persuade the world to get on board with Trump’s “maximum pressure campaign” against Iran, Pence went on to accuse Tehran of trying to recreate the Persian Empire by carving out a “corridor of influence” through Iraq, Syria and Lebanon.

The meeting in Warsaw is being used by the Trump administration to persuade the world to rally against Iran after President Donald Trump withdrew from the landmark 2015 Iran nuclear deal last year.

Other signatories of the deal — the U.K., France, China, Russia and Germany — have vowed to keep it alive and refused to comply with the Trump administration’s requests that they slap new sanctions on Tehran.

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Pence criticized Britain, France and Germany for unveiling a financial mechanism last month that the U.S. believes is meant to keep the nuclear deal alive by evading tough new American sanctions.

"Sadly, some of our leading European partners have not been nearly as cooperative," Pence said. "In fact, they have led the effort to create mechanisms to break up our sanctions."

The United Nation's atomic watchdog and U.S. intelligence chiefs have said Iran is still in compliance with the agreement despite the U.S. withdrawal.

While the administration had hoped to make the meeting a rallying cry for tougher action on Iran, the focus had to be widened and the emphasis on Iran softened after countries balked, three foreign diplomats told NBC News.

In a further rebuff to Washington, while the Warsaw meeting has been attended by more than 60 nations major European powers such as Germany and France refused to send their top diplomats.

Iran has denounced the gathering as an American anti-Iran "circus." Russia has said it would not attend.

During the speech, Pence said he and his wife would also visit Auschwitz, the Nazi concentration camp, later on Thursday to pay their respects to the "martyrs of the Holocaust."

"Anti-Semitism is not just wrong; it’s evil," Pence said.

Earlier Thursday, Secretary of State Mike Pompeo had told delegates that the world could not “achieve peace and security in the Middle East without confronting Iran.”

Iran has in the past called on Palestinians to rise up against Israel, and Iran’s supreme leader Ayatollah Khamenei has called Israel a “cancerous tumor.” Meanwhile, chants of “Death to Israel” and “Death to America” are not uncommon among ordinary Iranians protesting in the streets.

Israel has accused Iran of lying about its nuclear capabilities prior to signing the 2015 pact and considers a nuclear-armed Iran to be an existential threat. The country has also repeatedly sounded the alarm about Iran's influence in other parts of the Middle East.

Speaking at the conference on Wednesday, Israeli Prime Minister Benjamin Netanyahu startled Iranians and even the White House by calling for Israeli-Arab action against the government in Tehran that was translated by his office as urging “war with Iran.”

Israeli officials later tried to soften the reference by altering the English translation.