Iowa Senator Chuck Grassley is blasting a temporary agreement the U.S. has signed with Iran. Grassley says the deal poses a threat to America and its allies, though President Obama says, “I will do every single thing I can to resolve these issues without resorting to military conflict.” The agreement aims to freeze Iran’s disputed nuclear enrichment program, but Grassley says he’s concerned it leaves the door wide open.

Grassley says, “Considering Iran’s history, we have little reason to trust that country.” Grassley, a Republican, says the president’s deal leaves many questions unanswered and does too little to dismantle Iran’s nuclear enrichment program, which some fear could result in the production of atomic weapons. “I’m skeptical of Iran’s intentions,” Grassley says, “and I also fear that this deal will increase, not decrease, the threat to our country and even our allies in the region.”

The deal the U.S. signed with Iran and five other countries guarantees no new sanctions for six months, but Grassley says sanctions are exactly what’s needed. “I’m going to work with my Senate colleagues to preserve the pressure on Iran through new sanctions,” Grassley says. “It looks to me like there’s going to be a bipartisan approach to more sanctions for Iran.”

The temporary agreement is being referred to as a “historic mistake” by Israel’s Prime Minister Benjamin Netanyahu, and he’s pushing for a much-tougher final agreement. No one wants to see renewed U.S. military action in the Persian Gulf region, so Grassley says sanctions may be the best option. “It would send a clear signal to Iran, if they don’t negotiate in good faith, they’re going to get tougher sanctions instead of just the status quo,” Grassley says.

The agreement was reached last weekend between Iran and the U.S., along with Britain, China, France, Germany and Russia. Under the plan, parts of Iran’s nuclear program would be stopped and more international monitoring would be done, while some economic sanctions on Iran, as a reward, would be lifted.