UNITED NATIONS >> Iran’s president warned world leaders today that security in the energy-rich Persian Gulf could collapse quickly with a “single blunder,” and he accused the United States of engaging in “merciless economic terrorism” against his country.

On the same day as President Hassan Rouhani spoke, the U.S. ramped up oil-related sanctions on Iran, imposing penalties on six Chinese companies and their chief executives for continuing to transport Iranian crude.

Rouhani said in his speech to the annual U.N. General Assembly that the United States was engaging in “international piracy” against his country by re-imposing economic sanctions after Washington withdrew from the 2015 nuclear deal with world powers.

Iran “will never negotiate with an enemy that seeks to make Iran surrender with the weapon of poverty,” Rouhani said in his highly anticipated speech. “Stop the sanctions so as to open the way for the start of negotiations.”

Iranian state television broadcast Rouhani’s speech live across the country of 80 million people, many of whom are struggling under the weight of crippling U.S. sanctions that have sent the Iranian economy into freefall and limited Tehran’s ability to sell its oil abroad.

U.S. Secretary of State Mike Pompeo and the Treasury Department announced the latest sanctions, which freeze any assets the firms may have in U.S. jurisdictions and bar Americans from doing business with them,

“We’re telling China and all nations, know that we will sanction every violation of sanctionable activity,” Pompeo said at an event for United Against a Nuclear Iran, a lobby group opposed to the nuclear deal.

Tensions in the region have been increasing as the nuclear deal unravels under pressure from President Donald Trump. Iran has turned back to expanding its nuclear enrichment program after Trump’s decision last year to pull out of the accord and impose expansive sanctions on Iran despite that Tehran was in compliance with the nuclear deal.

The escalating crisis has raised concerns that direct conflict, with Iran at the center, could break out in the region — a scenario that all parties, including bitter rivals Iran and Saudi Arabia, have stressed they want to avoid.

The United States has sent military reinforcements and heightened its security presence in the Middle East in past months amid the rising tensions.

Rouhani’s remarks at the U.N. came a day after Trump described Iran as “one of the greatest threats” to the planet.

Although Rouhani’s manner during the speech was measured, the words he delivered were ominous.

“Our region is on the edge of collapse, as a single blunder can fuel a big fire,” he said, adding that it will become secure only when U.S. troops withdraw.

“Security shall not be supplied with American weapons and intervention,” he said. “Security cannot be purchased or supplied by foreign governments.”

Diplomatic efforts in Europe have scrambled to preserve the nuclear deal by searching, still unsuccessfully, for ways around the U.S. sanctions.

Rouhani said Iran has “only heard beautiful words.”

“It has now become clear for all that the United States turns back to its commitments and Europe is unable and incapable of fulfilling its commitments,” he said, warning: “Our patience has a limit.”

Just before his speech, the remaining signatories to the accord — Russia, China, Britain France, Germany and Iran — stressed they are trying to preserve it.

Still, Iran is finding itself increasingly squeezed and isolated. The European position appears to have shifted after a Sept. 14 attack on Saudi Arabia’s oil infrastructure, which jolted oil prices and temporarily knocked out nearly 6% of the kingdom’s daily global crude production.

In a joint statement, Britain, France and Germany joined the U.S. and Saudi Arabia this week in blaming Iran for the attack and in saying that the time had come for Iran to accept negotiations on its missile program and issues of regional security. These are two key areas that Trump says the nuclear deal did not address when it was completed under the Obama administration.

Iran has denied any involvement in the attacks on Saudi Arabia, and says any strikes by the U.S. or Saudi Arabia will lead to “all-out war.”

Rouhani also appealed to Iran’s neighbors, saying that their destinies are intertwined and stressing that Iran’s security is integral to regional security. The free flow of oil “could be guaranteed,” he said, when security in all areas for all the countries is provided.

He talked about Iran’s proposal for a Coalition for Hope, or the Hormuz Peace Initiative, that Tehran envisions would be formed under a U.N. umbrella and involve all of the region’s countries.

“Neighbor comes first; then comes the house,” he said. “We are neighbors with each other and not with the United States.”

The recent drone and missile strikes on the Saudi oil sites followed months of lower-level attacks on oil tankers and Iran’s shooting down of a U.S. surveillance drone over the Strait of Hormuz. The U.S. and its regional allies blame those attacks on Iran, which it also denies.

During his speech on Monday at the U.N., Trump left open the possibility of diplomatic engagement with Iran. As Rouhani ended his remarks, he also suggested there was still room for diplomacy.

“Let’s return to justice, to peace, to law, commitment and promise and finally to the negotiating table,” he said.