Russia has asked for 56 visas from the United States to allow Russian Foreign Minister Sergei Lavrov and his delegation to travel to New York for the annual gathering of world leaders at the United Nations this month, but so far has received none.

In a letter to U.N. Secretary-General Antonio Guterres, seen by Reuters on Friday, Russia's U.N. Ambassador Vassily Nebenzia said this was "alarming" because during the past several months Washington had "been constantly refusing to grant entry visas" to a number of Russian delegates for other U.N. events.

The United States takes seriously its obligations as U.N. host country, said a State Department spokesperson, adding that visa records are confidential under U.S. law so it could not comment on individual cases.

Under the 1947 U.N. "headquarters agreement," the United States is generally required to allow access to the United Nations for foreign diplomats. But Washington says it can deny visas for "security, terrorism, and foreign policy" reasons.

"We process hundreds of visas every year for Russian Federation delegates to U.N. events," said the State Department spokesperson, adding that applications should be submitted as early as possible to ensure timely processing.

"This is especially important because of Russia's unwarranted actions against our embassy in Russia, including the forced termination of local and third country national staff, which have severely limited our staffing and therefore our capacity to process visas," the spokesperson said.

Nebenzia said that the necessary applications had been submitted to the U.S. Embassy in Moscow.

A Guterres spokesperson did not immediately respond to a request for comment on Russia's letter.

The United States has long restricted Russian U.N. diplomats and visiting Russian delegations from traveling more than 25 miles (40 km) from New York City without Washington's prior approval.

In February, Washington slapped sanctions on Lavrov, accusing him of being "directly responsible for Russia's unprovoked and unlawful further invasion of Ukraine." The sanctions freeze any assets Lavrov may have in the United States and generally bar Americans from dealing with him.

The 56 visas requested by Moscow include an advance team of diplomats to prepare for the arrival of Lavrov and his delegation for the high-level meeting of the U.N. General Assembly in New York, which begins on Sept. 20.

Nebenzia added that no U.S. visas had yet been granted to journalists accompanying Lavrov and the flight crew.

Nebenzia cited some recent visa issues in his letter to Guterres, saying that Russia's Internal Affairs Minister Vladimir Kolokoltsev was unable to travel to New York for a U.N. Chiefs of Police summit this week.

He said representatives of Russian law enforcement agencies were also unable to attend a U.N. event this week on countering the use of information and communications technologies for criminal purposes.

"We would ask you to once again emphasize to the authorities of the United States that they must promptly issue requested visas for all Russian delegates and accompanying persons, including Russian journalists," Nebenzia wrote to Guterres.