UNITED NATIONS (Reuters) - Iran has accused the United States of abusing its position as the host of the United Nations by denying a visa to the Islamic Republic’s deputy foreign minister, according to a letter released on Friday.

Iran’s letter to the U.N. Committee on Relations with the Host Country said Deputy Foreign Minister for Legal and International Affairs Mohammad Mehdi Akhondzadeh Basti was repeatedly denied a visa by U.S. authorities.

In the letter, Iran’s U.N. Ambassador Mohammad Khazaee said Washington’s refusal to issue an entry visa to Tehran’s top official overseeing its relations with the United Nations kept him from attending events like the May 3-28 review conference on the nuclear Non-Proliferation Treaty, where Iran’s atomic program is a key topic of discussion.

Khazaee said U.S. authorities were misusing the country’s status as the seat of the United Nations headquarters “as political leverage to advance their political agenda against certain countries.”

He said it was “nothing short of calculated political intimidation and pressure” which he said “impairs the very foundations of multilateral diplomacy.”

In Washington, U.S. State Department spokesman P.J. Crowley declined to comment on Akhondzadeh Basti’s visa. “Visa decisions are confidential,” he told reporters.

Akhondzadeh Basti previously headed Iran’s diplomatic missions to Pakistan, Germany and the U.N. International Atomic Energy Agency in Vienna.

As the host of U.N. headquarters, the United States has pledged to issue entry visas to officials from U.N. member states, though it can and does deny entry permits to foreign officials for many reasons, such as failure to meet deadlines or provide proper documentation, or if espionage is suspected.

Washington issued Iranian President Mahmoud Ahmadinejad a visa to attend the opening of the nuclear arms treaty review conference earlier this month, though it has denied Iranian officials visas in the past, prompting complaints from Tehran.

The United States cut off diplomatic relations with Iran in 1980 during a hostage crisis. For the last eight years Washington and Tehran have been locked in an escalating standoff over Iran’s nuclear program, which Western powers fear is aimed at producing atomic weapons.

Tehran says its nuclear program is entirely peaceful and will produce electricity, not bombs.

Earlier this week the United States submitted a draft resolution to the U.N. Security Council that would impose a fourth round of U.N. sanctions against Iran for refusing to halt its enrichment program. The draft was agreed with Russia, China, Britain, France and Germany.