(CNN) - A bipartisan group of Senators is close to an agreement on tougher Iran sanctions in opposition to the White House, which is easing them as part of an interim accord Tehran struck with world powers aimed at curbing its nuclear ambitions, CNN has learned.
A Senate deal would include a new round of sanctions to begin in six months and would not allow for the enrichment of uranium. But it would permit commercial nuclear power as long as it was monitored by the international community.
The bipartisan group includes Democrats Chuck Schumer of New York and Robert Menendez of New Jersey and Republicans Lindsey Graham of South Carolina and Mark Kirk of Illinois.
"I hope this week we will introduce a bipartisan third round of sanctions," Graham told CNN in an interview on Monday.
"We'll do sanctions tied to the end game where the relief will only come if they stop the enrichment program, dismantle the reactor and turn over the enriched uranium."
But sources told CNN the group still has work to do to finalize its plan, and added the Obama administration is still very much opposed to additional sanctions.
"The administration's preference is for us to do nothing," said one source, while another said "they're fighting us tooth and nail."
President Barack Obama and Secretary of State John Kerry have said additional sanctions could undermine the interim deal struck last month in Geneva after delicate negotiation.
Obama said over the weekend that he would accept a peaceful nuclear program from Iran, including modest uranium enrichment.
Once a bipartisan deal emerges, the challenge will be to convince Senate Majority Leader Harry Reid to put it up for debate and a vote.
That would not be difficult with all Republicans likely to fall behind it and potentially a number of Democrats, too.
But the group may push for a promise to bring in up in January with the Senate racing to wrap up business before its holiday recess.
Last month, Iran agreed to limit its nuclear program in exchange for an easing of economic sanctions that have crippled its economy.
World leaders hope the six-month deal will pave the way to a long-term guarantee that Iran won't produce nuclear weapons.
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