Iranian authorities warned NATO member Bulgaria last month not to let the U.S. use its airports for planes participating in military operations in Iran, the foreign ministry said on Wednesday.

Earlier on Wednesday, Stanislav Balabanov, a deputy with the "There is Such People" party, showed a note from March 18 in which the Iranian government protested against U.S. military refueling planes parked at Bulgaria's Sofia Vasil Levski Airport.

In the note, Iran said it "reserves the right to take all necessary measures to protect its sovereignty, security and national interests in accordance with international law."

Later on Wednesday, in a statement to reporters, Deputy Foreign Minister Marin Raikov confirmed the note and said, "Bulgaria is not at war."

"No combat aircraft are being loaded over Bulgaria to participate in military operations," he told reporters. "We maintain intact diplomatic relations with the Iranian side."

In late February, Bulgarian media reported that several U.S. military planes landed at the Sofia civilian airport, and authorities have said they were part of the NATO forward deployment, which Raikov confirmed on Wednesday.

"Our parliament has not approved decisions to support relevant military actions in the Strait of Hormuz region," he said.

Some European countries, concerned over the war with Iran, have pushed back on U.S. military operations.

Spain closed its airspace and denied base access, Italy rejected a stopover at Sigonella base, and France blocked overflight of U.S.-Israel weapons flights.