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Iran’s Foreign Minister Mohammad Javad Zarif says that he was sanctioned by the United States after refusing an invitation to meet President Donald Trump at the White House in July.

Speaking at a press conference on Monday in Tehran, Zarif said that during his visit to the United Nations last month he met with several US senators and congressmen. Zarif said that he was warned that if he had accepted the invitation to the White House, he could have avoided the sanctions against him.

The minister said that he would not name the senators or congressmen he met with nor would he detail the contents of their conversations due to his role as a diplomat.

“On my trip to New York, I was told that I would be sanctioned within two weeks unless I accepted the offer, which I fortunately did not accept,” he said.

Iranian government spokesperson Ali Rabiei said on Sunday that an invitation was brokered by Senator Rand Paul, who Trump had authorized to act as an intermediary between the two countries, reported Iran’s state media Press TV. CNN has reached out to the White House and Paul’s office for comment.

On July 19, Trump told reporters: “Rand asked me if he could get involved. I said yes.”

The US sanctioned the outspoken Iranian foreign minister on Wednesday, following through on a weeks-old threat likely to elevate already heightened tensions with Iran.

Tensions in the Persian Gulf have escalated sharply in recent months, with Tehran seizing three tankers, the UK detaining an Iranian vessel off Gibraltar, and mysterious attacks on other oil tankers.

The US has also been building up its military presence in the Gulf, sending a carrier strike group, bomber and at least 1,000 additional troops to the region as it tries to organize an international military force to patrol the waterway. In July, Secretary of State Michael Pompeo said the US was justified in considering military action against Tehran.

In a statement last Wednesday, Treasury Secretary Steven Mnuchin said Zarif “implements the reckless agenda of Iran’s Supreme Leader, and is the regime’s primary spokesperson around the world.”

“The United States is sending a clear message to the Iranian regime that its recent behavior is completely unacceptable,” Mnuchin said.

Addressing the sanctions on Monday, Zarif said that “boycotting a country’s foreign minister means that your negotiations fell short,” and that the approach the US takes each day leads only to a failure in dialogue.

“The United States has not won any war in modern times and that is why they were forced to use sanctions and boycotts against Iranian institutions and organizations,” he added.

On Sunday, government spokesperson Rabiei stressed Zarif’s position as chief of foreign policy, diplomacy and security diplomacy, saying that “all diplomatic pathways must go through him,” Press TV reported.

“Is it anything but risible for a government to constantly claim to be open to negotiation and then place sanctions on the Foreign Minister of the very country that it invites to talks?” Rabiei said, according to Press TV.

CNN’s Nicole Gaouette, Kay Guerrero and Jennifer Hauser contributed to this report.