WASHINGTON – The Obama administration's nuclear accord with Iran has ramped up the pressure on several dozen senators who remain on the fence about additional sanctions on Tehran, including Minnesota Democrats Amy Klobuchar and Al Franken.

The pact with six world powers to cap Iran's long-disputed nuclear power program has sharpened divisions between Democrats who back the White House's diplomatic efforts and those who want to add more sanctions if the Islamic regime reneges on the six-month agreement.

While the debate has heated up in recent weeks, Klobuchar and Franken, who faces re-election this year, have remained largely out of the fray, saying they want to study the signals coming out of Iran and the U.S. partners in the negotiations.

The uncertainty has raised the stakes on the administration, which issued another veto threat over the weekend targeting bipartisan legislation drafted by New Jersey Democrat Bob Menendez threatening stiffer economic sanctions on Iran. At the same time, there's a sense in Congress that the mere threat of more sanctions is as good as a formal vote to approve them.

"I've been lobbied by everybody," Franken said in an interview Monday. "I'm telling everybody I have a pretty well-developed view of this. … And right now I don't think it's absolutely necessary for me to come down on one side or the other."

Klobuchar, in a written statement, also indicated that she has not made a decision. "Additional sanctions like the ones included in the Menendez bill may be necessary," she said, "and I will be meeting with the president and others to evaluate the legislation."

President Obama said the Senate bill, which reportedly has the backing of nearly 60 senators, could undermine months of delicate negotiations with Iran and make war more likely. "Imposing additional sanctions now will only risk derailing our efforts to resolve this issue peacefully," he said in a statement issued Sunday as the agreement with Iran was announced.

While Minnesota's senators remain undecided, the unrest among Democrats has long been on display. When the House voted 400-20 last July to toughen sanctions against Iran's nuclear weapons program, Minnesota Democrats Keith Ellison and Betty McCollum broke ranks and voted in the minority.

Ellison has said that any new sanctions would "kill any hope for diplomacy."

Republicans, meanwhile, are almost uniformly opposed to a deal that only freezes Iran's nuclear program, rather than dismantling it altogether. Most of the GOP leadership in the Senate has backed Menendez's bill, which would target banks and industries that helped Iran export oil if the regime violates the new agreement.

Among those pressing for an immediate sanctions vote by Congress is U.S. Rep. Michele Bachmann. The Minnesota Republican issued a statement Monday calling the new Iran accord a "dangerous agreement" that puts Obama "on the wrong side of history."

'A positive step forward'

Klobuchar called it "a positive step forward" to keep the pressure on Iran to live up to its international obligations.

Franken and Klobuchar both voiced support for the existing sanctions against Iran, which have crippled the nation's economy and, in the U.S. view, brought its leaders to the negotiating table. Franken credited the Obama administration for enforcing the sanctions "better than any administration before it." He also praised the White House for holding together the partnership of the United States, Russia, China, Britain, France and Germany.

Franken said that while the sanctions have worked, he understands the administration's argument that passing additional sanctions as the technical details of the deal are being worked out could strengthen the hand of Iranian hard-liners who want to go forward with their nuclear processing program without Western interference.

With or without a Senate vote to add to the existing sanctions, Franken said, "Iran knows that if this falls apart we will put extra sanctions on it. … They don't necessarily need this bill to be voted on and passed in order to know that."

Both Franken and Klobuchar have faced criticism from advocates of the nuclear accord with Iran, who see it as a historic breakthrough to avoid war and block Iran from becoming a destabilizing nuclear power.

William Davnie, a retired foreign service officer from Minneapolis, penned an opinion piece last week with Kate Gould of the Friends Committee on National Legislation arguing that Iranian hard-liners have already been handed ammunition by the unwillingness of more U.S. senators to stake out firm positions against additional sanctions.

"Minnesota is one of just 10 states where neither senator has taken a public position on whether or not to sign onto sanctions that would sink the deal — and risk another war in the Middle East," they wrote. They also noted that it would only take a few more backers to assemble a veto-proof majority for the Menendez bill.

But Franken suggested that the uncertainty could work both ways. "This is sort of a matter of judgment," he said. "In the past, the Congress has played bad cop to the White House's good cop for a more aggressive sanctions regime."

Follow Kevin Diaz on Twitter @StribDiaz.