NEW YORK (CBSNewYork/AP) — New York Sen. Charles Schumer, the only Democratic senator who’s come out so far against President Barack Obama’s nuclear agreement with Iran, is detailing his opposition.

The deal reached last month would curb Iran’s nuclear program in exchange for billions of dollars in relief from the economic sanctions.

Schumer said under the first 10 years of the agreement, Iran’s nuclear ambitions might be contained, but he warns the deal is open-ended after that, 1010 WINS’ Roger Stern reported.

“That means the United States and all the governments in the world say it’s OK for Iran to be a threshold nuclear state,” Schumer said Tuesday during his first local appearance since announcing he would oppose the Obama administration’s deal.

Schumer notes the agreement would release $50 billion in sanctioned money, which Iran could use to fund terrorism around the world, Stern reported.

“They’re going to use a lot of that money to create more trouble in the Middle East and the world,” Schumer said.

The alternative, Schumer said, is to go back to the bargaining table and come to a better agreement.

Even if the U.S. backs away and other countries lift their sanctions, Iran still will feel “meaningful pressure” from the U.S. penalties, Schumer said.

The senator’s view sharply contrasts with European leaders who have told U.S. lawmakers that if Congress were to reject the deal, the international sanctions would unravel, undermining global pressure on Iran.

He insists this was not a political decision, WCBS 880’s Peter Haskell reported.

“This is an issue of conscience,” Schumer said.

When asked by reporters whether he intended to lobby colleagues to vote with him, Schumer said “Certainly, I’m going to try to persuade my colleagues that my viewpoint is right, but anyone who thinks you can force somebody to vote with you in the Senate doesn’t understand the Senate.” he said.

“This is a vote of conscience. It was a vote of conscience for me. It will be a vote of conscience for my colleagues,” he added.

Schumer’s decision was a blow to the Obama administration after White House lobbying had produced a steady stream of support from Democrats.

The president has said the alternative to this deal is war.

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