美国有线新闻 CNN 美国伊朗舰船危险相遇 伊朗可能成为特朗普的难题（在线收听）

Unsafe encounters, that's how a U.S. military official describe some recent incidents in the Persian Gulf involving Iranian boats. Last month, seven Iranian fast attack boats reportedly harassed an American ship. The month beforehand, the U.S. Navy fired three warning shots after an Iranian boat came to close.

The U.S. called the Iranian maneuvers concerning, unsafe, and unprofessional. But they're just part of the reason why the Middle Eastern country could pose a significant challenge for the next U.S. president.

FREDERIK PLEITGEN, CNN SENIOR INTERNATIONAL CORRESPONDENT: The U.S. may have struck a deal with Iran over its nuclear program, but things are still tense.

Iran may be the biggest international headache for the next U.S. president for the following reasons. Iran will become much stronger militarily now that some sanctions are ended. And the stronger Iran still has a largely anti-American agenda. It's already causing military problems for the U.S. in places like Syria, Iraq and Yemen and diplomatic problems with Saudi Arabia and Israel.

Some hardliners in the U.S. and in Iran want to roll back the nuclear deal, which could destroy the improving relations between the two long-time rivals. Iran has also hinted that it could ramp up its uranium enrichment at any time and some experts fear the country may secretly be developing nuclear weapons regardless of the agreement.