Hassan Rouhani, Iran's president, pauses whilst speaking during a news conference in Tehran, Iran, on Monday, Oct. 14, 2019. Bloomberg | Getty Images

WASHINGTON — The U.S. will impose a fresh round of sanctions on Iran's largest shipping company and biggest airline, the nation's top diplomat announced Wednesday. Secretary of State Mike Pompeo targeted the Islamic Republic of Iran Shipping Lines, its China-based subsidiary, E-Sail Shipping, and Mahan Air, saying the companies are aiding the Iranian regime's alleged proliferation of weapons of mass destruction. "As long as its malign behaviors continue, so will our campaign of maximum pressure," Pompeo said Wednesday, adding that the transportation firms helped to "augment the regime's campaign of terror and intimidation at home and throughout the world." The sanctions on IRISL and E-Sail will take effect in 180 days in order to give customers who ship humanitarian goods time to adjust their contracts. The sanctions on Mahan Air, however, will take immediate effect. Earlier this year, Germany and France announced a ban on Mahan Air, in part, alleging the firm transports Iranian weapons and personnel to Syria.

An airplane of Mahan Air sits at the tarmac after landing at Sanaa International Airport in the Yemeni capital on March 1, 2015. Mohammad Huwais | AFP | Getty Images

"The Iranian regime uses its aviation and shipping industries to supply its regional terrorist and militant groups with weapons, directly contributing to the devastating humanitarian crises in Syria and Yemen," Treasury Secretary Steven Mnuchin said in a statement. "Aviation and shipping industries should be vigilant and not allow their industries to be exploited by terrorists." Iranian President Hassan Rouhani said Wednesday that Tehran will overcome U.S. sanctions. "The government is determined to defeat (the enemy) by bypassing America's sanctions ... or through various means including talks," the semi-official Iranian news agency ISNA quoted Rouhani as saying. Former Defense Secretaries Leon Panetta and James Mattis weighed in on the Trump administration's tumultuous relationship with Rouhani at the annual Reagan National Defense Forum. "Bottom line is, they are dangerous; we need to try and get them to the negotiating table. I don't think what we are doing now is working very effectively to get that done," Panetta said. Mattis, a four-star Marine Corps general, reiterated the importance of working with allies, an issue that prompted his shock resignation as Trump's Secretary of Defense. "We can't even deal with the nuclear threat alone and think we are going to somehow neuter this problem. It's going to take allies and partners, as almost every problem we face in the world takes allies and partners," he said. "Unilateral [doesn't] work, we've got to do this in concert with others," Mattis said, adding that the U.S. should take more creative approaches in dealing with Iran.

US President Donald Trump speaks as Defense Secretary James Mattis (L) looks on during a meeting with senior military leaders in the Cabinet Room of the White House on October 5, 2017. Mandel Ngan | AFP | Getty Images