WASHINGTON — An Iranian airline, backed by the country's notorious Revolutionary Guard and used to ferry weapons and fighters to support Syria's government, has acquired rights to fly commercial routes in more than a dozen European and Asian countries despite U.S. terror-related sanctions.

The agreement Iran and six other world powers signed last year ended some of the sanctions that had punished and isolated Iran for its nuclear program. But sanctions for ballistic missile research, terrorism, human rights violations and money laundering remain in place.

Mahan Air, the country's second-largest carrier, is under terror-related sanctions. The U.S. has accused the company of providing “transportation, funds transfers and personnel travel services” to the Revolutionary Guard's elite Quds Force, flying them and weapons to Syria to train Hezbollah militants, Syrian army troops and others.

Many countries honored the U.S. terror sanctions and blocked Mahan Air. But weeks before the nuclear deal was signed in July 2015, the airline announced it was launching a route to Munich — its second German destination. A wave of new routes to 15 countries followed, including France, Russia, China and Italy. France and Denmark were added in June 2016, and talks continue to add more routes in Europe.

A U.S. Treasury official told The Associated Press that the U.S. has been trying to get those countries to cooperate with U.S. efforts to block the airline's financial network, but has met with stiff resistance.

Washington doesn't want to restrict travel to and from Iran, the official said, noting that the country's main carrier, Iran Air, can fly around the world since the nuclear deal was implemented in January. The official was not authorized to discuss the issue publicly and spoke on condition of anonymity.

“By letting Mahan in, the Europeans are forgoing a critical pressure tool they have in their arsenal of nonmilitary coercive measures to pressure Iran and (Syrian President Bashar) Assad,” said Emanuele Ottolenghi, an Iran expert at the Center on Sanctions and Illicit Finance at the bipartisan Foundation for Defense of Democracies.

But the U.S. has no leverage to change EU laws allowing Mahan in. All it can do is ask the countries to ban Mahan and go after companies providing services to the airline, including banks, baggage handlers and cargo and freight companies.

A spokeswoman for the European Union said Mahan Air is not under EU sanction and the U.S. has no jurisdiction.

In 2014, the European Commission allowed those deemed safe commercial air transport operators — including Mahan Air — to fly to, from or within the EU.

The EU has also ignored U.S. terror sanctions and last week lifted its own on Bank Saderat, which Washington accuses of transferring money to groups it considers terror organizations, such as Hezbollah's militant wing and Hamas.

Mahan Air officials in Tehran declined to give an interview.