Prime Minister Binyamin Netanyahu tried to cancel a January briefing for U.S. Senators by Mossad Head Tamir Pardo, reports Time, citing sources familiar with the events.

The head of the Senate Foreign Relations Committee, Tennessee Republican Bob Corker, had requested the Jan. 19 briefing for six of his colleagues traveling to Israel “so that the intelligence agency, Mossad, could warn them that a Senate proposal might inadvertently collapse the talks,” the report says.

After Netanyahu’s office struck the meeting from the trip schedule, Corker allegedly “threatened to cut his own Israel trip short in protest,” and Netanyahu relented after the intervention of Israeli ambassador to the US, Ron Dermer.

Besides Corker, the Senate delegation included Republican Senators John McCain, Lindsey Graham and John Barrasso, Democratic Senators Tim Kaine and Joe Donnelly, and Independent Senator Angus King.

A bill proposed by Republican Mark Kirk and Democrat Robert Menendez would have imposed new sanctions on Iran if it didn’t agree by June 30 to a long-term deal on its nuclear program. US intelligence officials had concluded that the bill could cause the talks with Iran to collapse, according to a report on Bloomberg View. Corker, says Time, wanted the Mossad briefing to support the US assessment.

During the Mossad briefing, Pardo reportedly warned that the Kirk-Menendez bill would be like “throwing a grenade” into the US-Iran diplomatic process. He later released a statement saying he had used the phrase not to oppose new sanctions, but “as a metaphor” to describe the effect derailing the Iran talks might have.

A senior Israeli official then delivered an uncommonly harsh attack on US President Barack Obama’s administration calling the American claims that Pardo opposed sanctions “fraudulent.” He added that Israel had gone over the minutes of the meeting between Pardo and the delegation of senators, and that Pardo had not said what was attributed to him.

“Leaking the Mossad Head’s statements, even if they had not been falsified, is a serious breach of all the rules,” the senior source added. “Friends do not behave like this. Information from a secret meeting must not leak out.”

Since the Mossad briefing, Corker has been pushing a bill that would only impose new sanctions if Iran walked away from the November 2013 agreement that it signed.