U.S. Secretary of State Hillary Clinton on Wednesday expressed concern about allegations that some Latin American drug trafficking organizations are linked with Hezbollah and Iran.

"We are concerned about the activities of Iran and Hezbollah in the Western Hemisphere," the top U.S. envoy told the House Committee on Foreign Affairs at a hearing.

Washington brands Hezbollah, a Shiite militant group in Lebanon, as a terrorist organization, while Iran's disputed nuclear program is putting it on a collision course with Washington and its allies.

"We continue to monitor the situation closely. We are aware of and concerned about allegations that some Latin American drug trafficking organizations are linked with Hezbollah and Iran," Clinton said, vowing to take "appropriate action" to counter any threat that may arise.

Acknowledging that Washington has not found information to verify "a lot of the allegations," Clinton drew attention to Iran' s attempted assassination of the Saudi ambassador to the United States, a case unveiled by U.S. authorities in October 2011, calling it "a very large question mark and wake up call."

"We are continuing to look for direct links and we are engaged very extensively with our partners in the hemisphere, both to educate them about the dangers posed by Iran and Hezbollah and also to work with them to heighten our intelligence sharing," she said.

Citing the support of Argentina, Brazil, Mexico and Chile for a recent resolution of the International Atomic Energy Agency, which called on Iran to address concerns about its nuclear program, Clinton claimed that Washington is building "a very strong international and hemispheric coalition" against any efforts by Iran and Hezbollah in the hemisphere.

On the January tour of Venezuela, Nicaragua, Cuba and Ecuador by Iranian President Mahmoud Ahmadinejad, Clinton said "Our analysis of what happened is that it fell very far short of what the Iranians had hoped for."