U.S. Reportedly Denies Visa To Iran's Foreign Minister

The US denied a visa to Iranian Foreign Minister Javad Zarif, preventing him from attending a UN Security Council meeting in New York. Zarif criticized the decision on Twitter, suggesting the US fears the truth. The 1947 UN headquarters agreement generally requires the US to allow foreign officials to attend such meetings, but the US can refuse visas for security, terrorism, or foreign policy reasons. This incident occurs amid heightened tensions following the killing of Iranian General Qasem Soleimani.

What reasons can the US provide for refusing to issue visas?

What event has escalated tensions between the US and Iran?