The United States and its British and Canadian allies are preparing to roll out a coordinated set of sanctions against Iran on Monday amid growing concern that Tehran is pursuing a nuclear weapon, sources tell ABC News.

U.S. officials familiar with the plans say they target Iran’s nuclear sector as well as plugging key gaps that have allowed Iran to work around existing sanctions on its energy and financial sectors. The United Kingdom and Canada are both expected to announce unilateral measures to limit Iran’s access to their economies, with the UK essentially cutting off Iran’s access to its financial sector.

European Union ministers are expected to meet on December 1 to consider their own sanctions.

Two U.S. officials, who spoke on the condition of anonymity given the diplomatic sensitivities involved, say the State Department will sanction Iran’s petrochemical industry, which is normally used to produce products like plastic and styrofoam but is increasingly used to refine petroleum, as international sanctions have constrained the capacity of Iran’s energy sector. The new measure aims to discourage foreign companies from investing in that industry because it could inadvertently aid Iran’s energy sector and undermine previous sanctions.

The State Department is also expected to target both foreign and Iranian entities, many controlled by the Revolutionary Guard Corps, that have begun to help out with critical tasks in Iran’s oil and gas sector, picking up the slack as foreign companies pull out for fear of running afoul of sanctions.

A State Department spokesman declined to comment for this story.

The Treasury Department, meanwhile, is expected to issue a finding that the Iranian financial system is a “jurisdiction of primary money laundering concern.”

The finding, made under section 311 of the USA Patriot Act, enables the Secretary of the Treasury to require American banks to conduct additional reporting to ensure their corresponding foreign accounts are not indirectly dealing with Iran. That extra vigilance, officials say, will have a cascade effect where foreign financial institutions are more reluctant to do business with Iran.

The State Department and Treasury Department are also expected to designate additional Iranian entities for their role in Iran’s nuclear program.

A Treasury Department spokeswoman also declined to comment for this story.

The United States and its allies have long feared that Iran has been pursuing a nuclear weapon under the guise of a civilian nuclear energy program. Those fears were reinforced by a new report by the Director General of the International Atomic Energy Association earlier this month, which for the first time sounded the alarm about “possible military dimensions to Iran’s nuclear program.”

The report detailed “credible” evidence that Iran has been covertly developing a nuclear weapon design and testing components. It said Iran has built computer models to study the explosion of a nuclear bomb and is working to develop detonation devices. The report said Tehran has also built a containment vessel in which it can conduct explosive experiments and is studying how to mount a nuclear warhead on its Shahab-3 long-range missiles.

Iranian officials have dismissed the report. On Tuesday, one senior Iranian official called it “laughable.”

The IAEA report reignited calls on Capitol Hill and from prominent Republicans like presidential candidate and Texas Gov. Rick Perry for the Obama administration to sanction the Iranian Central Bank, a move they say would cripple Iran’s economy and its ability to pursue a nuclear weapon. Last Thursday, House leaders including Speaker John Boehner and Minority Leader Nancy Pelosi sent a letter to President Obama urging him to sanction the Central Bank.

Despite the renewed pressure, sanctions on the Iranian Central Bank and bans on Iran’s oil and gas sector will not be included in this latest round, according to one U.S. official, citing fears that such measures could lead to a spike in oil prices that would harm America’s own economic recovery.

The United States and its allies have resorted to unilateral sanctions as other multilateral routes to pressure Tehran have been blocked. U.S. and European officials say they would like to pursue additional sanctions against Iran in the United Nations Security Council, something they have successfully done four times in recent years, however they have been met with resistance by veto-wielding Russia and China.

European countries are reportedly pursuing their own additional sanctions, though officials say none are expected to be part of Monday’s coordinated announcement.

British Foreign Secretary William Hague tipped his hand about Monday’s planned action earlier this month when he told Parliament that his government was preparing financial and energy sanctions against Iran.

“We’re in discussions about increasing this pressure and we’re also considering further unilateral measures should Iran fail to comply with their responsibilities. And while I can’t go into precise detail now on the sanctions we are considering, we are looking at additional measures against the Iranian financial sector, the oil and gas sector, and the designation of further entities and individuals involved with their nuclear program,” he said shortly after the IAEA report was issued.

A spokesman for the British embassy in Washington did not reply to requests for comment. A spokesman for the Canadian embassy in Washington declined to comment.