Connecticut Sen. Richard Blumenthal said Thursday that he’s been listening to both supporters and opponents of the multi-national, nuclear non-proliferation agreement that’s been struck with the government of Iran. But the state’s senior senator wouldn’t say whether his Jewish heritage would play a part in his own decision to support or oppose the deal.

The agreement, which is waiting on Congressional approval, was between Iran on one side and the United States, China, France, Russia, Germany and the United Kingdom on the other. The deal would force Iran to develop nuclear power for peaceful purposes only for the next 15 years, and would allow monitors to verify that fact at the development sites themselves.

Blumenthal is the only member of Connecticut’s Washington delegation who has yet to announce a position about the deal, repeating during an interview Thursday that a decision could be expected within weeks.

Rep. Elizabeth Esty, D-5th District, issued her support for the deal late last week.

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Blumenthal also is one of three Jewish senators to remain undecided on the deal. Sen. Al Franken, D-Minn., became the fifth of nine Democratic Jewish senators to openly, though cautiously, support the agreement, writing an op-ed for CNN earlier in August.

“It isn’t a perfect agreement,” Franken wrote. “But it is a strong one. This agreement is, in my opinion, the most effective, realistic way to prevent Iran from getting a nuclear weapon anytime in the next 15 years.”

Besides Blumenthal, among Democratic Jewish senators, only Ron Wyden, of Oregon, and Ben Cardin, of Maryland, have not come down on either side of the debate.

Sen. Charles Schumer, D-N.Y., is the only Jewish Democratic senator to openly break with the administration and oppose the agreement. When he did so, he specifically mentioned the destabilizing effect the deal would have on the Middle East.

“For years, Iran has used military force and terrorism to expand its influence in the Middle East, actively supporting military or terrorist actions in Israel, Syria, Lebanon, Yemen, Iraq, and Gaza,” Schumer wrote in a release. “That is why the U.S. has labeled Iran as one of only three nations in the world who are ‘state sponsors of terrorism.’ Under this agreement, Iran would receive at least $50 billion dollars in the near future and would undoubtedly use some of that money to redouble its efforts to create even more trouble in the Middle East, and, perhaps, beyond.”

Lobbyists both for and against the Iran agreement have been targeting Blumenthal in anticipation of his decision. For example, former senatorial and gubernatorial candidate Ned Lamont has sponsored a series of ads and a Facebook page asking residents to “Contact Senator Blumenthal and urge him to vote yes on the Iran nuclear agreement.”

On the other side, Secure America Now, a conservative nonprofit group with a focus on foreign policy, urges residents to “Call Senator Blumenthal now and tell him to stand up for America and strike down this bad deal with Iran.”

Secure America Now lists former Arkansas governor and current Republican presidential candidate Mike Huckabee, among others, as a member of its board of directors.

Blumenthal, whose father, Martin Blumenthal, was a Jewish immigrant from Frankfurt, said Thursday during a telephone interview that his decision will be based on what he believes to be “our national interest.”

“My decision will be based on my judgement, as a matter of conscience and conviction,” he said.

Israeli Prime Minister Benjamin Netanyahu has been vocal in his own opposition to the deal. Though other senators and representatives demurred, Blumenthal was in attendance when Netanyahu addressed Congress before a deal had been reached.

“The prime minister’s concerns may well lead to greater care and caution in assessing a deal if and when an agreement is reached,” Blumenthal said in March. “My view continues to be that any agreement must be completely verifiable, comprehensive, air-tight, and long lasting. If there is no deal, stronger sanctions and other possible action should all be on the table.”

But Blumenthal would not discuss how the proposed deal may or may not be in Israel’s best interests.

“I’m not going to talk about how it works for any of our allies or partners,” he said. “My conclusion will be based preeminently on my judgment on what best serves the interest of our nation.”

Jordan Fenster can be reached by or @JordanFenster on Twitter.