President Trump and Turkish President Recep Tayyip Erdoğan quietly sought to arrange a meeting between senior U.S. and Iranian officials in Istanbul this week amid Israel's escalating war with Iran.

• But the effort collapsed when Iran's supreme leader — in hiding due to fears of assassination — couldn't be reached to approve it, according to three U.S. officials and a source with direct knowledge of the matter.

Why it matters: New details of this back-channel effort reveal the extent to which Trump was pushing for a direct meeting with the Iranians — even offering to attend himself, if necessary — in hopes of striking a nuclear deal and avoiding U.S. military intervention.

• In the days since, Trump and senior White House officials became less confident that a diplomatic solution was possible — and more convinced the U.S. would have to join the war to eliminate the Iranian nuclear program, according to U.S. officials.

Driving the news: Trump reiterated on Friday that he will make a decision on whether to join the war in the next "two weeks," saying he wanted "time to see whether or not people come to their senses."

• "I'm giving 'em a period of time. We're gonna see what that period of time is. And I would say two weeks would be the maximum," Trump told reporters.
• On Saturday evening, Trump is expected to convene his national security team in the White House Situation Room to discuss the war between Israel and Iran, which has entered its ninth day.

Behind the scenes: Trump received a phone call from Erdoğan on Monday while meeting with G7 leaders in Canada.

• Erdoğan proposed hosting a meeting in Istanbul the next day between U.S. and Iranian officials to explore a diplomatic solution to the war, three U.S. officials and a source with direct knowledge told Axios.
• Trump agreed and told Erdoğan he was willing to send Vice President Vance and White House envoy Steve Witkoff — and even travel to Turkey himself to meet with Iranian President Masoud Pezeshkian — if that's what was necessary to get a deal, the sources said.
• A White House official said that in the hours before the call from Erdoğan, Trump received "signals" from the Iranians through other back channels that they wanted to meet.
• While Trump's personal involvement was discussed, the official said, the more serious plan was to send Vance and Witkoff.

Erdoğan and Turkish Foreign Minister Hakan Fidan then relayed the proposal to Pezeshkian and Iranian Foreign Minister Abbas Araghchi, the sources said.

• Two U.S. officials said Pezeshkian and Araghchi tried contacting Iran's Supreme Leader Ayatollah Ali Khamenei to get his approval. But Khamenei, who has been in hiding for fear of being assassinated by Israel, couldn't be reached.
• After several hours, the Iranian side informed the Turks they couldn't get Khamenei's sign-off. Turkey then told the U.S. the meeting was off, a U.S. official said.

Shortly afterward, Trump took to Truth Social and posted an extraordinary public message to Khamenei.

• "Iran should have signed the 'deal' I told them to sign. What a shame, and waste of human life. Simply stated, IRAN CAN NOT HAVE A NUCLEAR WEAPON. I said it over and over again! Everyone should immediately evacuate Tehran!" Trump wrote.

• A senior White House official said the breakdown in talks wasn't the sole reason for the post and stressed there was "no direct correlation."
• The official added that Trump's call for civilians to evacuate Tehran — a city of 10 million people, with 17 million in the wider metropolitan area — reflected his desire to protect Iranian lives.

State of play: In recent days, the Iranians have said both publicly and privately that they will not negotiate directly with the U.S. unless Israel halts its attacks.

• Trump said Friday that it will be "very hard" to pause the war to allow for direct negotiations with the U.S., noting that Israel is "doing well" in its efforts to take out Iran's nuclear program.
• On Saturday, Erdoğan met with Iran's Foreign Minister Araghchi in Istanbul and urged him to hold direct talks with the Trump administration.
• Erdoğan told Araghchi that Turkey was ready to facilitate such talks as soon as possible, according to a statement from the Turkish president's office.

What to watch: On Saturday morning, six B-2 stealth bombers departed from their base in Missouri and began heading west, according to flight tracking data.

• The B-2s are expected to play a key role in any potential U.S. strike on Iran, capable of carrying the 30,000-pound "bunker buster" bombs likely to be used to destroy the heavily fortified Fordow uranium enrichment facility.
• The Pentagon referred questions to the White House.
• Trump said on Friday that Israel has "very limited capacity" to damage Fordow. "They can break through a little section, but they can't go down very deep. They don't have that capacity. And, we'll have to see what happens. Maybe it won't be necessary," Trump said.