BEIRUT (Reuters) – A senior commander in Iran’s Revolutionary Guards warned the United States on Monday that if it designated the group a terrorist organization and applied new sanctions its action could be perilous for U.S. forces in the region.

U.S. officials said earlier this year that President Donald Trump’s administration was considering a proposal that could lead to potentially categorizing the powerful Revolutionary Guards as a terrorist organization.

In Mid-June the U.S. Senate voted for new sanctions on Iran over its ballistic missile program and other activities not related to the international nuclear agreement reached with the United States and other world powers in 2015.

To become law, the legislation must pass the House of Representatives and be signed by Trump.

“Counting the Revolutionary Guards the same as terrorist groups and applying similar sanctions to the Revolutionary Guards is a big risk for America and its bases and forces deployed in the region,” said Armed Forces Chief of Staff Major General Mohammad Baqeri, according to Sepah News, an official news site of the Guards.

He did not give details on what form of risk he foresaw for U.S. forces and bases.

The Revolutionary Guards are the most powerful security force in Iran, overseeing vast economic holdings worth billions of dollars and wielding huge influence in its political system.

Baqeri said on Monday that Iran’s missile program was defensive and would never be up for negotiation, according to Sepah News.

Three days after the U.S. Senate voted on the new sanctions, Iran fired missiles into eastern Syria, targeting bases of Islamic State which had claimed responsibility for attacks in Tehran which killed 18 people.

The Revolutionary Guards are fighting in Syria against militant groups which oppose President Bashar al-Assad.

Baqeri was also critical of recent remarks by U.S. Defense Secretary James Mattis that regime change would be necessary before the United States could normalize relations with Iran.

“American officials should speak a little more wisely, thoughtfully and maturely about other countries, particularly a powerful country like Iran which has stood against all plots with strength and pride,” he said, according to Sepah News.

(Reporting By Babak Dehghanpisheh; Editing by Richard Balmforth)