Israel is believed to be spying on nuclear talks between the P5+1 and Iran, the Wall Street Journal reported on Monday.

According to the report, US officials discovered the spying right after talks kicked off between Tehran and the US, UK, Russia, China, France and Germany.

Intelligence gathering by Israel is reportedly aimed at a greater Israeli initiative of building a case against any emerging bad deal. Israeli intelligence officials gathered information by listening in on “confidential US briefings, informants and diplomatic contacts in Europe.”

US senior officials told the Journal that the White House was not initially concerned about the spying. However, when the Israeli government used classified negotiation information to garner support of US lawmakers, many in the Obama administration felt that boundaries had been crossed.

“It is one thing for the US and Israel to spy on each other. It is another thing for Israel to steal US secrets and play them back to US legislators to undermine US diplomacy,” an unnamed senior US official stated.

The question, however, that begs asking is how did the US discover the Israeli espionage? By spying on Israel as well.

US spies listened in on conversations between Israeli officials and determined, based on certain insider information, that the information could have only been gleaned by espionage.

Israel has denied any allegations that it spied on closed-door talks on the Iranian nuclear program. A senior official from the Prime Minister’s Office told CNN on Tuesday, “These allegations are utterly false. The State of Israel does not conduct espionage against the United States or Israel’s other allies.”

Israeli Foreign Minister Avigdor Liberman told Army Radio on Tuesday that Israel did not spy on the US during nuclear talks, but hinted that they may have kept a close eye on the Iranian instead.

“I think this report is not correct, not accurate,” he stated. “Of course, Israel has various security interests, and it is clear that we have good intelligence services. But we don’t spy on the United States.”

Liberman added, “There are enough participants involved [in the nuclear talks], such as the Iranians. We got our intelligence from other sources, not from the United States. The instruction has been clear for decades now: you don’t spy on the United States, directly or indirectly.”

The spying revelation comes on the heels of US Secretary of State John Kerry’s return to Switzerland for a final push in negotiations with his Iranian counterpart, Mohammad Javad Zarif.

Kerry, along with other Western negotiators, will return to Lausanne on Thursday as the March 31 deadline to agree to an outline of a nuclear agreement draws near.

On Monday, Israeli Intelligence Minister Yuval Steinitz warned that nuclear negotiators are nearing an outcome that will result in a “bad deal” as part of last-ditch efforts to save negotiations.

“We think it’s going to be a bad, insufficient deal,” he told Reuters while in France. “It seems quite probable it will happen, unfortunately.”