US has denied a visa to Iranian Foreign Minister Mohammad Javad Zarif that would have allowed him to attend a UN Security Council meeting in New York on Thursday, a US official said.
Monday's comments by the official, who spoke on condition of anonymity, came as tensions escalate between the two countries.
This is after the Washington killed Iran's most prominent military commander, Qassem Soleimani, in Baghdad on Friday.
Under the 1947 UN "headquarters agreement," the US is generally required to allow access to the UN for foreign diplomats. But Washington says it can deny visas for "security, terrorism and foreign policy" reasons, Reuters reported.
The US State Department declined immediate comment.
Iran's mission to the UN said: "We have seen the media reports, but we have not received any official communication from either the US or the UN regarding Foreign Minister Zarif's visa".
Meanwhile, Iran on Sunday dropped all limitations on its uranium enrichment. This is another step back from commitments under the deal, which US President Donald Trump.
Trump has vowed to strike 52 Iranian targets, including cultural sites, if Iran retaliates with attacks on Americans or US assets.