TEHRAN, Iran — A senior Iranian lawmaker warned Russia that its delay in delivering an anti-aircraft missile defense system to Tehran could harm relations between the two countries, state television reported Sunday.

“If they do not fulfill their promise, this will be a negative point in relations between the two countries,” said Alaeddin Boroujerdi, head of the parliament’s national security and foreign policy committee.

Boroujerdi said more delays “will be harmful to Russia since we have many areas of cooperation with them.”

Russia signed a contract two years ago to sell the S-300 surface-to-air missiles to Iran but has not made any deliveries or given any explanation for the delay. The United States and Israel strongly oppose the deal because it would significantly boost Iran’s air defense capabilities at a time of heightened tension over the country’s nuclear program.

The S-300 surface-to-air missiles are capable of shooting down aircraft, cruise missiles and ballistic missile warheads at ranges of over 145 kilometers and at altitudes of about 27,500 meters.

In 2007, Russia delivered Iran another anti-aircraft system called the Tor-M1, which can hit aerial targets at up to 6,000 meters.

Russia and the U.S. are among six nations leading an effort to ensure that Iran does not use what it maintains is a civilian nuclear program to develop an atomic bomb. But Moscow also has close ties with Iran and is helping build its first nuclear power plant, forcing Russia into a delicate balancing act.

In the international talks over Iran’s nuclear work, a UN-brokered plan worked out in October requires Tehran to send 1.2 tons of low-enriched uranium — about 70 percent of its stockpile — to Russia by the end of the year for further enrichment.