DENVER (AP) – Sen. Cory Gardner says he has serious reservations about the outlines of an agreement with Iran over its nuclear program.

The Colorado Republican also says Congress should vote on whether to approve the deal, a point of contention between lawmakers and President Barack Obama.

READ MORE: Firefighters Discover A Body In Colorado Springs While Putting Out A Fire

Gardner spoke Monday after returning from a weeklong trip to five Middle East nations as part of a congressional delegation. He said Iran’s nuclear program was a worry in each country.

READ MORE: Agriculture Secretary Tom Vilsack Commends Aurora Public Schools On Free Meal Program

He says he’s concerned the deal leaves Iran with too much infrastructure in place that could be used to build a nuclear weapon.

Gardner, a freshman, was one of 47 Republican senators who signed a letter to Iran’s leaders in March warning any nuclear deal they make with Obama could expire when he leaves office.

MORE NEWS: Denver Weather: Chilly And Wet For One More Day In Colorado

(© Copyright 2015 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)