President Trump called the Iran nuclear deal a “horrible agreement for the United States” in response to Israeli Prime Minister Benjamin Netanyahu's bombshell allegations about Tehran's covert activity – but stopped short of saying whether he'd abandon the deal ahead of a looming deadline.

The president addressed the claims during a Rose Garden press conference Monday afternoon, moments after Netanyahu held a dramatic presentation revealing intelligence he says shows Iran is lying about its nuclear weapons program.

“That is just not an acceptable situation,” Trump said.

Trump said Netanyahu’s claims show Iran is “not sitting back idly."

"They're setting off missiles which they say are for television purposes," Trump said. He added: "I don't think so.”

White House Press Secretary Sarah Sanders responded, “The United States is aware of the information just released by Israel and continues to examine it carefully. This information provides new and compelling details about Iran’s efforts to develop missile-deliverable nuclear weapons. These facts are consistent with what the United States has long known: Iran had a robust, clandestine nuclear weapons program that it has tried and failed to hide from the world and from its own people. The Iranian regime has shown it will use destructive weapons against its neighbors and others. Iran must never have nuclear weapons.”

Trump has repeatedly expressed a desire to exit the Iran deal, which was signed during the Obama administration. A crucial deadline for re-certifying the deal is on the horizon.

Netanyahu clearly intended for Trump to see his presentation, as he noted that Trump would soon make a key decision on the Iran deal.

“I’m sure he’ll do the right thing,” Netanyahu said.

On Monday, Trump suggested he could seek to negotiate a new agreement, something he discussed during French President Emmanuel Macron’s visit to Washington last week.

“So we'll see what happens,” Trump said, when asked about the announcement. “I'm not telling you what I'm doing. [A lot] of people think they know. And on or before the 12th, we'll make a decision.”

The president made the comments during a joint press conference with visiting Nigerian President Muhammadu Buhari.

Trump said that overall, “what we've learned has really shown that I have been 100 percent right.”

Netanyahu said during his earlier presentation that new intelligence shows Iran lied about never having nuclear weapons and lied again by not coming clean under the terms of the 2015 deal. "The Iran deal ... is based on lies," he said.

The information was obtained within the past 10 days, Israeli officials told Fox News. Netanyahu said the files were moved to a "highly secret" location in Tehran, and contained materials spread over 55,000 pages and 55,000 files on 183 CD's.

"The nuclear deal gives Iran a clear path to producing an atomic arsenal," Netanyahu said Monday.

NETANYAHU SAYS IRAN ‘BRAZENLY LYING’ AFTER SIGNING NUCLEAR DEAL

Netanyahu's statement came on the heels of a missile attack in northern Syria that killed nearly 26-pro-government fighters, mostly Iranians, according to a Syria war monitoring group. Israel had no comment on the strike, but there was widespread speculation that Israel was behind it. Tehran has sent thousands of Iran-backed fighters to back Assad's forces in Syria's seven-year civil war.

Speaking to reporters at the Pentagon on Monday, Defense Secretary Jim Mattis said the United States “had nothing to do with the strike last night.”

Mattis also said the evidence cited by Netanyahu on Monday did not come up during his discussions with the Israeli minister of defense last week. But he said parts of Iran nuclear deal “certainly need to be fixed.”

“The Iran Deal was and has always been a foreign policy debacle. But today’s stunning intel presentation from @netanyahu provides even more troubling context. All along it was built on a crumbling foundation of lies, deception, and naivete. This 'deal' should be shredded,” House Freedom Caucus Chairman Mark Meadows, R-N.C., tweeted.

Israel and Iran are arch-enemies, and Israel has said repeatedly it would not allow Iran to establish a permanent military presence in Syria. Iran, which is backing the forces of Syrian President Bashar Assad, has accused Israel of carrying out another airstrike in Syria this month that killed seven Iranian military advisers and vowed revenge.

“That is just not an acceptable situation." — President Trump

U.S. Secretary of State Mike Pompeo on Sunday ratcheted up the Trump administration's rhetoric against Iran and offered warm support to Israel and Saudi Arabia in their standoff with Tehran.

"The United States is with Israel in this fight," Pompeo said.

The 2015 deal gave Iran relief from crippling sanctions in exchange for curbs on its nuclear program.

Netanyahu has been a leading critic of the agreement, saying it fails to prevent Iran from gaining nuclear weapons capability and welcoming Trump's pledges to withdraw from the deal if it is not changed.

Both Trump and Netanyahu say the deal should address Iranian support for militants across the region and Iran's development of long-range ballistic missiles, as well as eliminate provisions that expire over the next decade.

On Monday, Iran's Supreme Leader Ayatollah Ali Khamenei said the time when Iran's enemies can "hit and run" is over.

"They know if they enter military conflict with Iran, they will be hit multiple times," he said, according to his website. He did not specifically refer to the latest attack in Syria.

Trump on Monday also floated the idea of holding his planned summit with North Korean leader Kim Jong Un in the Demilitarized Zone that divides the Koreas.

"There's something that I like about it because you are there, you are actually there," Trump said. "If things work out there's a great celebration to be had on the site, not in a third-party country."

A Trump-Kim meeting would be the first U.S.-North Korean leadership summit in more than six decades of hostility since the 1950-53 Korean War. Trump has previously said that five locations were being considered, but on Friday said the choice had been narrowed to two or three.

Monday was the first time he'd publicly specified potential locations for the meeting, slated for May or early June. He added that the Southeast Asian city state of Singapore was also in the running.

Fox News' Travis Fedschun, Lucas Tomlinson, Yonat Friling in Jerusalem, Mike Emanuel, Serafin Gomez and The Associated Press contributed to this report.