DUBAI, United Arab Emirates (AP) — Iran's supreme leader vowed Thursday in a defiant tone to protect the Islamic Republic's nuclear and missile capabilities, which U.S. President Donald Trump has sought to curtail through airstrikes and as part of a wider deal to cement the war's shaky ceasefire.

In a statement read by a state television anchor, Ayatollah Mojtaba Khamenei said the only place Americans belonged in the Persian Gulf is "at the bottom of its waters" and that a "new chapter" was being written in the region's history. Khamenei has not been seen in public since taking over as supreme leader following the killing of his father in the war's opening airstrikes.

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His remarks come as Iran's economy is reeling and its oil industry is being squeezed by a U.S. Navy blockade halting its tankers from getting out to sea. The world economy is also under pressure as Iran maintains its chokehold on the Strait of Hormuz, through which a fifth of all crude oil is transported. On Thursday, the global benchmark for oil, Brent crude, traded as high as $126 a barrel.

That shock to oil supplies and prices is putting pressure on Trump, who is floating a new plan to reopen the critical passageway used by the U.S.'s Gulf allies to export their oil and gas.

Under the plan, the U.S. would continue its blockade on Iranian ports, while coordinating with allies to impose higher costs on Iran's attempts to subvert the free flow of energy, according to a senior administration official.

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Trump is weighing multiple diplomatic and policy options to push Iran to end its chokehold, said the official, who spoke on condition of anonymity because they were not authorized to comment publicly.

The new proposal, first reported by The Wall Street Journal, is Trump's latest effort to persuade other nations to help reopen the strait.

Ceasefire shaken as strait remains shut

The U.S blockade is designed to prevent Iran from selling its oil, depriving it of crucial revenue while also potentially creating a situation where Tehran has to shut off production because it has nowhere to store oil.

A recent Iranian proposal would push negotiations on the country's nuclear program to a later date. Trump said one of the major reasons he went to war was to deny Iran the ability to develop nuclear weapons. Iran long has maintained its program is peaceful, though it enriched uranium at near-weapons-grade levels of 60%.

Pakistan on Thursday said it was still facilitating indirect talks between the U.S. and Iran aimed at easing tensions, but Islamabad would also welcome direct communication between the two sides, even by phone.

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"If the two parties can engage in real-time conversations, that could ease the sticking points," said Ministry of Foreign Affairs spokesperson Tahir Andrabi at a weekly news briefing. He declined to share details of any Iranian or U.S. proposals.

Speaking to mark Persian Gulf Day in Iran, Khamenei's remarks signaled that nuclear issues and Iran's ballistic missile program wouldn't be traded away.

"Ninety million proud and honorable Iranians inside and outside the country regard all of Iran's identity-based, spiritual, human, scientific, industrial and technological capacities — from nanotechnology and biotechnology to nuclear and missile capabilities — as national assets, and will protect them just as they protect the country's waters, land and airspace," Khamenei said.

Khamenei referred to America as the "Great Satan," a long hurled insult by Iranian leaders toward the U.S. since the 1979 Islamic Revolution. He said Americans should have no business in the Persian Gulf.

"Foreigners who come from thousands of kilometers away to act with greed and malice there have no place in it — except at the bottom of its waters," said Khamenei, who was reportedly was wounded in the Feb. 28 attack that killed his father, the 86-year-old Supreme Leader Ayatollah Ali Khamenei.

Khamenei signals strait will remain shut

In his remarks, Khamenei seemed to signal Iran would maintain its control over the waterway, which sits in the territorial waters of Iran and Oman. Iran had been charging some ships reportedly $2 million apiece to travel through the strait.

He said that Iran's control of the Strait of Hormuz will make the Gulf more secure, and that Tehran's "legal rules and new management" of the strait will benefit all the region's nations.

However, the world considered the strait an international waterway, open to all without paying tolls. Gulf Arab nations, chief among them the United Arab Emirates, have decried Iran's control of the strait as akin to piracy.

Madhani reported from Washington. Associated Press writers Munir Ahmed in Islamabad and Amir Vahdat in Tehran, Iran, contributed to this report.