The Middle East remained in a tense limbo on Tuesday after President Trump said he had postponed a major attack on Iran to give more time for diplomacy.

Iran did not immediately respond directly to Mr. Trump’s remarks, which were made on Monday. An Iranian Army spokesman, Brig. Gen. Mohammad Akraminia, warned on Tuesday that any American attack would prompt Iran to open “new fronts” using “new tools and methods,” according to IRNA, Iran’s state news agency.

As the monthlong cease-fire has come under increasing strain, Pakistan, a mediator in the conflict, has sought to keep indirect talks alive between Tehran and Washington. Iranian state media reported that Pakistan’s interior minister, Mohsin Naqvi, had met Iran’s foreign minister, Abbas Araghchi, in Tehran on Monday evening, and discussed efforts to end the war.

The Pakistani government has not commented on the two-day trip, which reportedly started on Sunday. Tasnim, an Iranian semiofficial news agency, described Mr. Naqvi’s visit to Tehran as part of Pakistan’s efforts to “facilitate dialogue and promote regional peace.”

Mr. Trump said on Monday that he had authorized a “very major attack” against Iran for Tuesday, but had postponed it after the leaders of Qatar, Saudi Arabia and the United Arab Emirates asked for more time to pursue an agreement over Iran’s nuclear program. He said there was a “very good chance” that a deal could be reached, but that the U.S. military was prepared for a “full, large scale assault” if Iran did not agree to terms acceptable to Washington.

The episode was the latest example of Mr. Trump’s brinkmanship over Iran, in which threats of overwhelming force have repeatedly given way to last-minute pauses for diplomacy.

Negotiations have stalled over Iran’s nuclear program and the Strait of Hormuz, a critical transit point for oil and gas, which Iran has effectively closed since the early days of the war, rattling global energy markets.

Mr. Trump has demanded that any agreement prevent Iran from obtaining a nuclear weapon, while a U.S. military official has said that Iran has used the cease-fire to dig out bombed ballistic missile sites, move mobile launchers and adjust its tactics for any resumption of strikes.

The war, now in its third month, has hit Iran hard but U.S. military officials say the Iranian government has demonstrated resilience and the ability to impose heavy costs on the wider region and the global economy.

Elian Peltier and Leily Nikounazar contributed reporting.