President Trump will decline to certify the Iran nuclear deal on Friday through a process that will leave the agreement intact while inviting Congress to weigh in on new restrictions against Tehran.

The White House hopes the resulting U.S. policy toward Iran will expand beyond its current dependence on the Joint Comprehensive Plan of Action, as the Iran deal is formally known, and involve a broader look at Iranian aggression.

But the approach Trump will lay out on Friday could allow the debate over how best to counter Iran to languish in a divided Congress, which could force Trump to continue observing a deal he described last month as an "embarrassment" to the U.S.

"We think the agreement is weak. It leaves areas unaddressed," Secretary of State Rex Tillerson told reporters at the White House Thursday evening.

Tillerson, who advocated internally to preserve the deal in the weeks of debate that preceded Trump's decision, said the strategy Trump will unveil will call on Congress to address areas where the nuclear agreement is silent.

Such blind spots include Iran's support for groups, such as the Houthis in Yemen or Hezbollah, that destabilize the region, as well as its repeated ballistic missile tests. Those kinds of aggressions have drawn condemnation from the U.S., but don't technically violate the nuclear deal.

"We will stay in the JCPOA, but the president is going to decertify" the deal using the Iran Nuclear Agreement Review Act, Tillerson said on Thursday.

Congress passed INARA, also known as the Corker-Cardin law, in order to exert some oversight over the Iran deal in 2015 amid criticisms of the Obama administration's unilateral pursuit of the deal. Corker-Cardin requires the administration to certify to Congress Iran's compliance with the agreement every 90 days — a deadline that forced Trump's hand this week and brought about his announcement.

That legislation gives the president several grounds on which to decertify the deal, and Trump is expected to rely on one that examines whether the continued suspension of sanctions in exchange for limits on Iran's nuclear enrichment and centrifuges remains in the interest of U.S. national security.

Tillerson said Trump would ask Congress to consider amending the Corker-Cardin law so that it encompasses more of Iran's bad behavior, a step the U.S. government could take without consulting the European allies who would bristle at any attempt to change the JCPOA itself.

"The amendment to INARA is something that doesn't require us to negotiate anything with anyone else," Tillerson noted.

The secretary of state said Congress has "three rough alternatives" to the status quo once Trump declares the deal counter to U.S. interests. One, which some Iran hawks have feared, is for lawmakers to do nothing after Trump gives them the option to reimpose sanctions. Another, Tillerson noted, would involve voting to revive sanctions, a move that would effectively nullify the agreement.

The third path, which the administration will ask Congress to consider, would amend the Iranian Nuclear Review Act to include "trigger points," or specific non-nuclear behaviors that could prompt the re-introduction of sanctions.

"While it's complex in terms of thinking about various outcomes ... the decision itself is not that complex," Tillerson said. "Once that decision is made that will guide, then, our diplomatic engagements."

Democrats have publicly expressed resistance to any effort that would weaken former President Obama's signature foreign policy achievement. They have maintained, among other things, that undermining the deal would hurt America's relationships with allies who signed onto the JCPOA under Trump's predecessor.

But Tillerson said his conversations with Democrats in the House and Senate had given him reason to hope that they would not automatically block an attempt to supplement the Iran deal with additional restrictions.

"In discussions we've had with the minority ... there's been interest in wanting to understand it and not an outright rejection of it," he said.

Supporters of the JCPOA argue that because Iran has not violated the letter of the agreement, the administration would have no standing to decertify its compliance with the deal.

Tillerson acknowledged that argument Thursday, noting material compliance is not the issue at the heart of Trump's efforts to layer the JCPOA.

"We don't dispute that they're in technical compliance," Tillerson said.

Administration officials said the Department of Treasury would also move to slap targeted sanctions on individuals and groups associated with the Islamic Revolutionary Guard Corps, a wing of Iran's armed forces that is often accused of supporting terrorism.