The 1947 United Nations Headquarters Agreement requires foreign diplomats access to the headquarters in New York even if those diplomats represent countries with whom the U.S. has unfavorable or strained relationships.
Citing "security, terrorism and foreign policy" reasons, the United States violated this agreement last week when it denied Iranian Foreign Minister Mohammad Javad Zarif a seat at the United Nations Security Council.
According to Iran's ISNA news agency, Zarif explained:
"What we know is that the U.S. State Secretary [Mike Pompeo], in a call to the Secretary General of the United Nations [Antonio Guterres], said: 'We did not have time to issue a visa for Mohammad Javad Zarif and we will not issue a visa'. The Secretary General responded by saying that it is Iran's right to take part in this session."
The Security Council meeting on upholding the UN Charter was scheduled before the recent military escalation between the U.S. and Iran after Donald Trump unilaterally ordered the assassination of Iranian military general Qassem Suleimani.
Zarif tweeted Monday:
"While U.S. displays utter contempt for UN Charter & its catastrophic adventurism encourages extremism and terror, tomorrow we'll host Tehran Dialogue Forum & discuss ways of achieving regional security, incl Hormuz Peace Endeavor #HOPE."
Secretary of State Mike Pompeo responded to reporters:
"I can't add much more to this issue of Foreign Minister Zarif's travel to the United States. I'll say only this: we will always comply with our obligations under the U.N. requirements and the headquarters agreement and we will do so in this particular instance and more broadly every day."
"The United States retains full control and authority over the entry of persons or property into the territory of the United States and the conditions under which persons may remain or reside there."
The United States sanctioned Zarif for implementing "the reckless agenda of Iran's Supreme Leader" before the September annual UN meeting, yet Zarif was still permitted to attend, as he was in April and July.
The Trump administration is having a hard time justifying how much of an "imminent threat" Qassem Suleimani was.
Sen. Chris Van Hollen (D-MD) tweeted a screenshot of a memo Trump circulated to senators attempting to justify Suleimani's murder: