President Trump on Wednesday promised new sanctions against Iran, and Iranian news media reported that American obstruction might force the country’s president to miss a major United Nations gathering, as the fallout from an attack on Saudi Arabia last weekend continued to build.
Saudi Arabia’s defense ministry said it would make public on Wednesday what it called evidence of Tehran’s responsibility for the multiple airstrikes Saturday against major oil processing facilities in the kingdom. The attack, using drones and possibly cruise missiles, had temporarily cut Saudi oil processing in half, shaking global markets.
Mr. Trump has already imposed punishing economic sanctions on Iran and some of its top officials, in what the administration has described as a “maximum pressure” campaign to force Iran to negotiate new limitations on its nuclear program and stop its sponsorship of militant groups across the Middle East.
On Wednesday morning, he wrote on Twitter that he had told the Treasury secretary, Steven Mnuchin, “to substantially increase Sanctions on the country of Iran.” It was not immediately clear how extensive the latest round of penalties would be, or whether they would be aimed at Iran generally, specific elements of the regime or individuals.
Mr. Trump and Iran’s president, Hassan Rouhani, have been expected to attend the annual United Nations General Assembly session in New York next week, and there was even speculation this summer about a possible face-to-face encounter between them.
But on Wednesday, the official Islamic Republic News Agency reported that an Iranian advance team had been unable to go to New York to prepare for the meeting because the United States had not granted visas. As a result, it said, Mr. Rouhani and his delegation might not attend the gathering, which runs from Tuesday through the following Monday.
Mr. Trump has said repeatedly that he is open to a meeting with Mr. Rouhani, which would be the first between leaders of the two countries after four decades of antagonism, but Mr. Rouhani has said that Iran would not agree until the United States lifted economic sanctions.
The attack on Saturday was the latest — and potentially the most serious — factor escalating tensions between the two countries, raising fears of military clashes and even outright war.
Iran and its ally, the Houthi rebel faction in Yemen, insist that the Houthis — who are fighting a Saudi-led coalition in Yemen’s civil war — carried out the strikes in retaliation for the extensive bombing by Saudi Arabia that has killed thousands of people in Yemen. The Houthis are known to use weapons supplied by Iran, but the attack showed a level of technological sophistication far beyond what the Houthis had demonstrated before.
American and Saudi officials have said that the weekend attack clearly used Iranian weapons. The Americans have also said that evidence that has not been made public points to a strike launched from Iran, to the north, not from Yemen, to the south.
The Saudi Defense Ministry scheduled a news conference Wednesday afternoon to present what it called “material evidence and Iranian weapons proving the Iranian regime’s involvement.” It was not clear whether that meant the kind of indirect involvement, through munitions and training, that Iran has had in previous Houthi strikes on Saudi Arabia, or something more direct, like Iranian personnel taking part or the attack’s having been launched from Iran.
Mr. Rouhani sent a formal note on Monday to the United States denying an Iranian role and warning that any American action against Iran would bring retaliation, Iranian state news media reported on Wednesday. The note went through Swiss envoys who act as go-betweens because the United States and Iran do not have diplomatic relations.
Secretary of State Mike Pompeo was scheduled to meet on Wednesday in Saudi Arabia with Crown Prince Mohammed bin Salman, the heir to the throne and the country’s day-to-day ruler, but it was not clear whether there would be any public announcement about the talks. In a statement, the State Department said the two would “discuss the recent attack on the kingdom’s oil facilities and coordinate efforts to counter Iranian aggression in the region.”
Mr. Trump tweeted on Sunday that the United States was “waiting to hear from the Kingdom as to who they believe was the cause of this attack, and under what terms we would proceed!”
Last year, the president withdrew the United States from the 2015 accord limiting the scope of Iran’s nuclear program, and reimposed sanctions that had been lifted as part of the deal. This year, Mr. Trump has hit Iran and Iranian officials with new rounds of sanctions.
The main penalties seek to choke off Iran’s international oil sales, the heart of its economy. They bar any company doing business with Iran from using the American banking system, whose reach is so vast that Mr. Trump’s actions apply to many overseas businesses.
After Mr. Trump began imposing more sanctions this year, several tankers were damaged near the Persian Gulf, and Western governments said they had been sabotaged by Iran, which Tehran denied. Iran has also seized several foreign vessels in or near the Strait of Hormuz, including a British-flagged tanker it has held for two months.
Analysts have described those incidents — and, possibly, the attack on Saudi Arabia — as one prong of a two-pronged strategy to pressure other nations to provide sanctions relief, by showing that Iran can interrupt world oil supplies. The other prong, analysts say, is that Iran began exceeding the limits on its nuclear program under the 2015 deal.