Iran's lawmakers are seeking to increase uranium enrichment under the country's nuclear programme to a level that can produce bomb-grade material, a state-run website said.
The bill introduced on Wednesday could bring Tehran into direct conflict with the major powers that reached an interim agreement with Iran in Geneva last month, requiring Tehran to suspend its enrichment of higher grade uranium.
Iran's most powerful authority, Supreme Leader Ayatollah Ali Khamenei, has so far backed the accord.
This draft bill has been prepared in reaction to America's hostile measures.
The lawmakers, irked by the foreign policy shift since moderate President Hasan Rouhani was elected in June, oppose the Geneva deal.
The bill, "if approved, will oblige the government to ... enrich uranium to 60 percent level in order to provide fuel for submarine engines if the sanctions are tightened and Iran's nuclear rights are ignored (by major powers)," said lawmaker Mehdi Mousavinejad.
It was not immediately clear whether or when parliament might discuss the bill.
The official IRNA news agency said it was introduced by some 100 lawmakers and had been tagged with a "double urgency" status, meaning it could be discussed in parliament within a week.
"The bill is aimed at giving an upper hand to our government and the negotiating team ... It will allow the government to continue our nuclear programme if the Geneva deal fails," IRNA quoted Hossein Taghavi Hosseini, spokesman for parliament's National Security and Foreign Affairs committee, as saying.
The November 24 accord is meant to give the United States, Russia, China, France, Britain, Germany and Iran a period of six months to negotiate a final settlement of the decade-old standoff, easing worries over a new war in the Middle East.
"Iran's parliament lacks power and particularly after Rouhani's election win, the hardline lawmakers do not have the upper hand," an unnamed senior western diplomat in Tehran told Reuters news agency.
"Iran's Supreme Leader backs the deal and ultimately, lawmakers have to follow his path."
The Iranian government would have no choice but to obey such a bill if passed by parliament.
But diplomats and analysts believe Iran could be using parliament as a bargaining tool in the talks.
"This draft bill has been prepared in reaction to America's hostile measures," Mousavinejad told the official IRNA news agency on Tuesday.