WASHINGTON — President Trump threatened Monday to destroy vital Iranian energy and water infrastructure if a peace deal is not reached, as Tehran continued to deny negotiations were taking place and said it was preparing for a ground invasion following the arrival of thousands of American troops in the region.

If a ceasefire agreement is not reached quickly, the president said in a social media post, “We will conclude our lovely ‘stay’ in Iran by blowing up and completely obliterating all of their Electric Generating Plants, Oil Wells and Kharg Island (and possibly all desalinization plants!).”

The threats came within hours of the president insisting on Sunday night that diplomatic efforts would “probably” lead to a deal soon, and that Iran had allowed 20 more oil cargo ships to pass through the Strait of Hormuz as a “sign of respect.”

Trump said the United States is in “serious discussions with A NEW, AND MORE REASONABLE, REGIME in Iran” but offered no details.

Iran, however, continued to throw cold water on the negotiations Monday when Esmail Baghaei, the foreign ministry spokesperson, dismissed the Trump administration’s terms as “unrealistic, unreasonable and excessive.”

“I do not know how many people in the United States take American diplomacy claims seriously. Our mission is clear, unlike the other side, which constantly changes its position,” he said in comments carried by the semi-official Iranian agency Tasnim News.

Baghaei said that there have been no direct negotiations, but only messages through intermediaries stating that the U.S. wants to confer.

White House Press Secretary Karoline Leavitt said at a news briefing on Monday that the “American people are smart enough” to not take Iranian officials “at their word” when they say there are no negotiations happening with the United States.

Leavitt said the Trump administration is negotiating with Iranian leaders who are “appearing more reasonable behind the scenes” than the regime’s previous leaders, who were killed by strikes launched by the United States and Israel.

“This is another historic opportunity for Iran to do the right thing to rid themselves of their nuclear ambitions and to come to a deal with this president,” she said. “Or, again, they will see the grave consequences of the United States armed forces.”

Leavitt added that Trump is “not afraid” to use the full force of the U.S. military to ensure victory in the Middle East. She said this after being asked why the president was threatening to intentionally target civilian infrastructure that could impact water and energy supplies, a move that could amount to a war crime under international law.

“Of course this administration and the United States armed forces will always act within the confines of the law, but with respect to achieving the full objective of Operation Epic Fury, President Trump is going to move forward unabated,” she said.

As the war continues and Arab countries are roped into the conflict, Leavitt told reporters, the president is open to having those countries help pay for the costs associated with the Iran war.

“I won’t get ahead of him on that,” she said. “But certainly it’s an idea that I know that he has and something that I think you’ll hear from him on.”

On Saturday, the USS Tripoli, a naval warship, arrived in the Middle East carrying about 3,500 sailors and Marines and a transport of fighter planes. Earlier this month, the San Diego-based USS Boxer and two warships from the 11th Marine Expeditionary Unit departed from Camp Pendleton to join the buildup of troops in the region.

The deployments have made Iranian diplomatic envoys even more dubious that American peace efforts are sincere.

“The enemy publicly sends messages of negotiation and dialogue while secretly planning a ground offensive. [They] are nothing more than a cover to hide preparations for a land invasion,” Iran’s top lawmaker, Mohammad Bagher Qalibaf, said in a statement Sunday.

He added that Iranian forces were waiting for the arrival of American troops on the ground to “set them on fire” and “punish their regional partners forever,” according to state media.

As officials in both Washington and Tehran strike increasingly hard lines, neighboring countries are desperate for a truce.

Egyptian President Abdel Fattah Sisi pleaded with Trump to stop the war during a speech at an Egyptian energy conference on Monday.

“I tell President Trump: Nobody can stop the war in our region in the gulf but you,” Sisi said.

“Please, Mr. President, please. Please help us stop the war. You are capable of doing so.”

Egypt, though not directly involved in the war, has contended with its repercussions on energy, fertilizer and food prices, not to mention disruptions to shipping income Cairo receives through the Suez Canal.

“Wealthy countries might be able to absorb this, but for middle-income and fragile economies, it could have a very, very severe impact on their stability,” ‌Sisi said, noting that predictions of oil reaching $200 per barrel were “not an exaggeration.”

Egypt and Israel signed a peace treaty in 1979, which saw Israel return territory it seized during the 1967 war. Though the agreement is deeply unpopular with most Egyptians, it has held despite escalating tensions during Israel’s campaign against Hamas.

In December, the two nations formally announced a $35-billion agreement expanding Israel gas exports to Egypt. But the war with Iran has disrupted supplies, tripling the cost of imports, according to Egyptian officials.

Last week, the government ordered energy-saving measures for a one-month period, including early closing times for most commercial establishments as well as reductions in street lighting and allocations for government vehicles.

Jordan, another U.S. regional ally that is also energy-starved, took similar steps, enacting bans on air conditioning in government offices and private use of government vehicles.

Despite talks of negotiations, the fighting showed little sign of abating.

Trump’s call for peace followed a fresh round of U.S. and Israeli airstrikes on Iran Monday. Tehran retaliated by hitting a major water and power facility in Kuwait, and Saudi Arabia and the United Arab Emirates said they intercepted incoming Iranian missiles.

Two U.N. peacekeepers were killed on Monday when an “explosion of unknown origin” hit their vehicle near the village of Bani Hayyan, in south Lebanon.

The deaths mark the second fatal incident in two days involving the United Nations Interim Force in Lebanon, known as UNIFIL, a peacekeeping force established in 1978 and which later monitored cessation of hostilities between the two nations.

UNIFIL also reported a peacekeeper was killed Sunday night when a projectile exploded in a UNIFIL position.

“We do not know the origin of the projectile. We have launched an investigation to determine all of the circumstances,” a UNIFIL statement on Monday said.

Meanwhile, Israel continued its bombardment of Lebanon, hitting areas near the capital and in the country’s south. One strike targeted a Lebanese army checkpoint, killing a soldier, the Lebanese military said. Lebanese authorities said on Monday that the death toll since hostilities broke out between Hezbollah and Israel earlier this month continues to rise.

The Israeli military said one of its soldiers was killed in a Hezbollah anti-tank missile attack in southern Lebanon, which also wounded four other soldiers. Six soldiers have been killed since Israel restarted its campaign in Lebanon.

Hezbollah rockets also killed two civilians, according to Israeli health authorities.

Israel’s fire and rescue service said a fuel tanker and a building at the oil refinery in the northern city of Haifa were hit by debris from an intercepted missile, according to a report from Israeli daily the Times of Israel.

It was unclear whether the missile was launched by Iran, the Lebanese Shiite group Hezbollah or Yemen’s Houthi rebels.

Deaths from the conflict continue to rise, with 1,900 people killed in Iran, over 1,200 in Lebanon, 19 in Israel and 13 U.S. military members. Millions of people have been displaced from their homes in Iran and Lebanon.

Ceballos and Quinton reported from Washington, Bulos from Beirut.