U.N. experts said in a report circulated Tuesday that not a single country has reported any violations of an arms embargo against Iran, possibly the result of a political decision to avoid any "negative impact" on negotiations to rein in Tehran's nuclear program.

The panel of experts monitoring sanctions against Iran said in the final report on its year-long mandate that the "drastic reduction in reporting and information-sharing" by governments could also reflect a reduction in Iran's efforts to buy banned materials.

But it cited several sanctions violations that were not reported and quoted some unnamed countries as saying Tehran's previous attempts to circumvent the bans remain basically unchanged.

The report's release coincided with the Security Council's unanimous approval of a resolution extending the mandate of the panel of experts until July 9, 2016. It came just three week before the June 30 deadline for Iran to reach a deal with six world powers that would put long-term caps on its present nuclear activities and lift some sanctions.

The Security Council has imposed four rounds of sanctions against Iran because of concerns it is seeking to develop nuclear weapons, and its refusal to suspend enrichment. Tehran claims its nuclear program is peaceful and exists only to produce energy for civilian use.

The sanctions, which have chipped away at Iran's economy, include a ban on the import of nuclear and missile-related materials and travel bans and the freezing of assets on listed individuals and companies.

The panel said the commitment by member states to implement sanctions has exerted "a definite influence" on the negotiations, noting the "high expectations of a final agreement."

While the panel said Iran has "implemented its commitments" under a deal with the six Western countries to curb its nuclear program in exchange for a limited easing of economic sanctions during the negotiations, its questioning of the failure to report any new violations in Tehran's procurement efforts is likely to raise questions in the United States and among its key European allies.

Although no country reported a travel ban violation, the panel cited media reports and published several photos of Maj. Gen. Ghasem Soleimani, commander of the elite Quds Force in Iran's Revolutionary Guard, showing that he traveled to Iraq, Syria and Lebanon.

Soleimani, who has been on the U.N. sanctions blacklist since 2007, "was reportedly organizing and training militia and regular forces in those countries," the panel said. He was also shown on a magazine cover as a commander fighting the Islamic State group in Iraq, it said.

The experts said they were investigating a report from an unnamed member state that an Iranian approached a company in January 2015 trying to buy compressors, which are used in the oil and gas industry but can also be used to extract enriched uranium from centrifuges that could be used to fuel nuclear missiles.

The experts said they haven't had time to investigate a report from Britain on April 20 that it "is aware of an active Iranian nuclear procurement network which has been associated with Iran's Centrifuge Technology Company and Kalay Electric Company," which is under U.N. sanctions.

Iran has also sent arms to Iraq, according to the report.

It said Massoud Barzani, president of Iraq's Kurdistan regional government, confirmed last August that Iran had supplied its fighters with weapons and ammunition, a period coinciding with the Islamic State extremist group's capture of swaths of territory in Iraq. It said Iran's Foreign Minister Mohammad Javad Zarif also confirmed sending equipment to Iraq. It also cited a recent media report quoting a U.S. official saying Iran sent Iraq advanced weapons including rockets and missiles.

The report lists arms shipments to Yemen dating back to 2009 -- including recent reported shipments to Houthi Shiite rebels fighting the country's government.

It also noted that Iran continues to demonstrate "special interest in high-grade machine tools" which have industrial applications but could also contribute to nuclear and missile activities.