President Trump’s cease-fire with Iran in June envisioned a broader deal to end the war and rein in the country’s nuclear program, all negotiated within 60 days.

But that deadline, set to pass on Monday, has been essentially abandoned, and the war has transformed into a contest of willpower and economic endurance that has no end in sight.

There have been no publicly reported U.S. strikes on Iranian targets since late July. Yet the effective collapse of the agreement underscores how Mr. Trump has struggled to end the war he started in February alongside Israel, and how far he remains from the ambitions of the June deal, including fully reopening the Strait of Hormuz, a critical waterway where Iran has choked off oil and gas shipping since the fighting began.

Those inside the White House are well aware that they will blow past Monday’s deadline and that the conflict has largely morphed into one of economic warfare, according to two Americans familiar with the negotiations.

The current strategy bears a striking resemblance to previous, yearslong U.S. attempts to isolate Iran in the hopes of compelling it to abandon its nuclear ambitions. The policy had mixed results, and some analysts are skeptical that even severe economic pressure on its own will force Iran to change course. After all, that was the approach Mr. Trump attempted in his first term, even though his Treasury secretary, Scott Bessent, said last week that he was about to impose financial penalties unlike any seen before.

The June memorandum of understanding was widely seen as a boon for Iran, granting the regime badly needed sanctions relief even as talks over tough concessions like nuclear enrichment were postponed for later. But Iranian leaders opted to escalate again rather than consolidate their gains from the deal, according to Nate Swanson, an Iran expert at the Atlantic Council, a Washington-based research group.

Ships could move through the Strait of Hormuz freely before the war. Iran’s insistence that the deal’s vague language on the issue gave it control over the waterway led to the deal falling apart. Iran began firing on ships that transited in channels outside Iranian waters, and American forces retaliated by bombing southern Iran, prompting a cycle of attacks and counterattacks across the Middle East.

Now, Iran refuses to reopen the strait until the United States follows through on its commitments from the cease-fire, like releasing frozen Iranian assets abroad. The Trump administration wants Iran to first end the blockade, said Ali Vaez, an Iran expert at the International Crisis Group, a research institute.

“Neither side is really ready to finalize a deal. They both think that in a matter of days or weeks, the other side will be more desperate for a deal, so they’ll be able to get more out of it,” Mr. Vaez said. “This is why we are locked into this game of endurance again.”

On Saturday, the United Arab Emirates’ state-owned oil company announced that another of its vessels had come under attack in the waterway. It did not say who was responsible, but it has previously blamed Iran for attacks on its ships.

Reopening the strait has increasingly become Mr. Trump’s main focus in the conflict, even though he initially said the war was meant to empower the Iranian people to overthrow the existing regime, severely degrade its missile capability and stop Tehran from getting a nuclear weapon.

There has been little indication that Iran and the United States have extensively discussed the Iranian nuclear program since the cease-fire in June, let alone formulated a deal that could satisfy both sides.

Abbas Araghchi, the Iranian foreign minister, said over the weekend that Iran had yet to decide whether to resume talks with the United States. But the 60-day timeline was no longer relevant, he added, given that the June agreement was essentially defunct.

“We did not have a cease-fire that now needs to be extended,” Mr. Araghchi said. “We had an end to the war, which has now taken on a new status.”

Former U.S. officials who worked on Iran say the prospect of a new nuclear deal between the United States and Iran within 60 days was always remote, although the agreement provided for extensions. A previous, Obama-era, agreement took about two years of delicate talks to negotiate. Mr. Trump withdrew from that deal, called the Joint Comprehensive Plan of Action, in 2018.

The Trump administration hoped that the June agreement would, at the very least, open the Strait of Hormuz. But to get the deal over the line, they relied on vague language that lent credibility to Iran’s claim to dominate future shipping in the waterway, analysts said.

“It was a flawed document; it was hurried out when it wasn’t ready for prime time,” said Mr. Swanson, the Iran expert. “And they didn’t resolve the most important short-term issue, which was the strait.”

Instead, the United States and Iran now seem to be settling in for an indefinite struggle, neither at all-out war nor in a defined peace. Seeking to force Iran to accept U.S. terms, the Trump administration has brought back sanctions on Iranian oil and reinstated a naval blockade, both of which were temporarily canceled by the agreement.

Iran’s strained economy, which prompted mass protests that were brutally crushed early this year, is a major consideration for Iranian decision makers. But Mr. Swanson argued that the current stalemate was more likely to push Iran toward escalation than toward conciliation.

While there has been little progress on the commitments outlined in the agreement, Mr. Trump and his Iranian counterparts have continued to exchange a war of words.

During an event in Garden City, N.Y., on Friday, Mr. Trump appeared once again intent on changing the narrative, saying he would soon be “declaring the Hormuz Strait a territory of the United States.”

It was not clear how serious Mr. Trump’s proposal was. But doing so could involve deploying boots on the ground and almost certainly would require a prolonged Navy presence — moves antithetical to the “America First” values of Trump supporters who want an end to prolonged military conflicts overseas.

Mr. Trump has also been known to toss out half-baked ideas on foreign policy to redirect attention and scrutiny, like when he shocked the world last year by proposing a U.S. takeover of the Gaza Strip, an idea that never materialized.

The White House on Saturday did not respond to questions over whether the administration had developed actual plans to take control of the Strait of Hormuz. Mr. Trump’s aides also did not respond to questions over the approaching Monday deadline.

Iranian officials, in turn, have defied Mr. Trump as they push their own demands — including one that they had not made before war.

“Accept reality once and for all. So far, you have suffered major strategic defeats,” Kazem Gharibabadi, the Iranian deputy foreign minister, said on social media. “The Strait of Hormuz has been Iranian, is Iranian, and will remain Iranian.”