Choosing a new car is rarely an easy decision: a buyer must consider all sorts of factors, including cost, safety, color, and gas mileage. Unfortunately, there’s another factor consumers should consider when buying a car today: whether the maker has business relationships with the Iranian regime.

We write as two concerned Americans and car lovers who are appalled by the dangerous and direct ties the auto industry continues to maintain with the regime that controls Iran — the same regime that sponsors terrorists, kills U.S. troops, brutalizes its own citizens, and is illegally pursuing a nuclear weapon.

By selling and producing cars in Iran, the world’s auto manufacturers aren’t just contributing to the Iranian treasury; they’re contributing to the regime’s nefarious ends. For example, the regime uses Volvo trucks to transport missiles, Mercedes as ballistic launch platforms, and Nissan SUVs to ferry Mahmoud Ahmadinejad around Tehran. Iran’s leaders rely on the auto industry both as a massive source of revenue and as a means of accessing advanced technologies and products for its military and security forces.

It is indeed impossible for an automaker to do responsible business in Iran, as having a presence there requires partnering with the government. Following an almost complete takeover by the regime, the industry is controlled by state-owned entities intent on securing foreign technology and funds. Iran’s two dominant automakers — Iran Khodro and Saipa — are both subsidiaries of IDRO, a sanctioned government conglomerate that is closely tied to the Revolutionary Guard Corps (IRGC) and responsible for the development of the regime’s nuclear and ballistic missile programs. Iran’s third largest auto-manufacturer, the Bahman Group, is nearly 50 percent owned by the IRGC.

Given this situation, it is both dangerous and irresponsible for automakers to remain in Iran. United Against Nuclear Iran (UANI) has extensively pressured these companies, and this year UANI joined New York City Public Advocate Bill de Blasio in launching “IranWatchList.com” and a corresponding consumer action campaign to pressure automakers active in Iran. When UANI and the Public Advocate launched this site in March, there were 13 major offenders: Fiat, Hyundai, Isuzu, Kia, Mazda, Mitsubishi, Nissan, Peugeot, Porsche, Renault, Suzuki, Toyota, and Volvo.

Shortly thereafter, both Hyundai and Porsche made the responsible decision to end their business in Iran. Then, in May, Fiat followed, ensuring that its Iveco trucks would no longer be sold to Iran’s military. Also recently joining this list is Kia Motors, whose “Pride” model once accounted for 30-40 percent of all vehicles on Iran’s roads.

These were commendable actions, and the Iranian auto sector is already feeling the effects of the pressure from the U.S. and its allies. According to industry data, auto production in Iran was down 66% last month compared to one year ago, and 42% for the whole year.

It’s now time for the other companies to get on board, and stop helping fuel Iran’s economy and lining the mullahs’ pockets. A particularly concerning case is occurring now with Peugeot, which said it “suspended” its deliveries to Iran in February, yet since March 2012 has had more than 100,000 of its vehicles produced there. Significantly, UANI has called on General Motors (GM) to get involved in this matter given that GM recently began a close financial partnership with Peugeot, and is now a part-owner. Peugeot’s fellow French auto manufacturer Renault has notably increased its production in Iran, doubling its output from 2010 to 2011.