Iranian ‌President Masoud ⁠Pezeshkian said Sunday that the country would "never bow down to the enemy," vowing that the ruling Islamic Republic regime would "defend national interests with strength."

"If talk of dialogue or negotiation arises, it does not mean surrender or retreat," he said in a message posted on social media before President Trump rejected Iran's response to the latest U.S. peace proposal. 

"The goal is to uphold the rights of the Iranian nation and to defend national interests with resolute strength," said Pezeshkian.

Iran is prepared to fight "whenever it is necessary," foreign ministry spokesperson Esmail Baqaei said Monday, adding that the regime would also continue using diplomacy, "whenever we deem it appropriate."

Speaking to reporters Monday, Baqaei was asked how Iran would respond if the U.S. were to launch new attacks on the country.

'We fight whenever it is necessary," he said. "Whenever we deem it appropriate, we use diplomacy as a tool to secure the interests of the Iranian nation."

Baqaei said Iran had "shown that it is serious about pursuing its national interests and legitimate rights" through a "diplomatic processes in good faith and in a reasonable manner."

"The other side must prove itself," he said, referring to the U.S. "It must demonstrate that it is serious in this regard. So far, it has failed."

He earlier said Iran had not demanded any concessions in its response to the latest U.S. peace proposal: "The only thing we demanded was Iran's legitimate rights."

President Trump dismissed Iran's response on Sunday as "totally unacceptable." 

President Trump is expected to fly to Beijing on Wednesday for a summit with his Chinese counterpart Xi Jinping, and the Iran war is likely to be on the agenda.

Mr. Trump is under mounting pressure to end the war and calm energy markets that have sent fuel prices spiraling upward for two months. He's expected to try to lean on President Xi to use his influence with Tehran to get them to agree to a deal.

"I would expect the president to apply pressure" over Iran, a senior administration official speaking on condition of anonymity told reporters Sunday, according to the French news agency AFP. The official said Mr. Trump had raised concerns about China continuing to bolster state coffers in Iran and Russia by purchasing oil - despite U.S. sanctions - "multiple times" during phone calls with Xi, as well as China's sales of military-civilian dual-use goods.

"I expect that conversation to continue," the official said.

U.S. sanctions against Chinese entities over the Iran war are also likely to come up, the official told AFP.

Iran's foreign ministry spokesperson Esmail Baghaei voiced hope on Monday that China would instead use the visit to reinforce Tehran's positions and push back on U.S. demands for a peace agreement.

"Our Chinese friends know very well how to use these opportunities to warn about the consequences of the U.S.' illegal and bullying actions on regional peace and security," he said, "as well as on economic stability and international security."

CBS/AFP

Iran's Foreign Ministry said Monday that it had called for an end to the war across the region and the release of frozen Iranian assets abroad in its response to the latest U.S. peace proposal, which President Trump rejected on Sunday.

"We did not demand any concessions. The only thing we demanded was Iran's legitimate rights," said ministry spokesman Esmaeil Baqaei said Monday during a weekly briefing.

He said Tehran's demands included "an end to the war in the region," ending the U.S. naval blockade of Iran's ports and vessels, and the "release of assets belonging to the Iranian people, which have for years been unjustly trapped in foreign banks."

Mr. Trump on Sunday rejected the Iranian response as "totally unacceptable."

"Our focus is on what is urgent," Baqaei said Monday. "What is urgent is ending war in all its forms, including in Lebanon." 

Baqaei said Iran was also keen to ensure "safe maritime navigation in the Persian Gulf and the Strait of Hormuz" while "stopping illegal actions and acts of maritime interference by the United States against commercial vessels."

Iran's approach is, he said, "very responsible and reasonable … to prioritize immediate issues and focus on resolving them, rather than discussing topics whose history shows they have, on at least two occasions, led to war."

The Trump administration has insisted so far that any peace deal include a commitment by Iran to severely curb, if not completely end its nuclear enrichment program.

CBS/AFP

President Trump branding Iran's terms for ending the Middle East war "totally unacceptable" raised the possibility of renewed hostilities and sent oil prices sharply higher in early Asia trade on Monday.

President Trump said on his Truth Social platform that he "just read the response from Iran's so-called 'Representatives.' I don't like it — TOTALLY UNACCEPTABLE!"

Global energy markets were unnerved with no indication of an imminent agreement to end the war and to reopen the shipping lanes of the Strait of Hormuz. The price of a barrel of international benchmark Brent crude was back above $100 a barrel early Monday.

The benchmark U.S. oil contract West Texas Intermediate also surged back toward the $100 a barrel mark ahead of Monday morning trade, as investors braced for further disruptions to supplies through the strait, where Tehran has imposed a near total blockade.

CBS/AFP

The shaky ceasefire in the Iran war was tested again Sunday when a drone caused a small fire on a ship off the coast of Qatar, while the United Arab Emirates and Kuwait reported drones entering their airspaces.

The UAE blamed Iran for the latest attack, the latest threat to a month-old ceasefire, which the Trump administration says is still in effect.

There were no casualties reported, and no one immediately claimed responsibility.

CBS/AP