President Trump plans to take a first step Friday toward gutting the Iran nuclear agreement, though aides said he is willing to consider an additional deal that would pressure Tehran to prove it has given up the means to make nuclear weapons.

While Trump will formally announce his decision to back out of the multinational agreement, he will also ask Congress not to re-impose economic sanctions right away; instead, he will call for new requirements on Iran in an effort to "fix" the agreement he has long criticized, aides said.

Trump faced a Sunday deadline to certify the agreement. Every 90 days, the president must certify that Iran is in compliance of the deal. If Trump decertifies it, it would be despite Secretary of State Rex Tillerson saying Iran has "technically" held up its end of the bargain.

"Let's see if we can address the deficiencies that exist within this agreement," Tillerson said in a briefing for reporters.

Tillerson added that "we may be unsuccessful," and "we may not be able to fix the deal." He added that Trump himself is "not particularly optimistic" about the prospect.

The U.S. signed the agreement in 2015 along with Russia, China, Germany, France and Great Britain. The European signatories have have urged Trump to re-certify it and questioned whether Iran would go along with any new provisions.

Under the agreement, the U.S. and allies reduce sanctions on Iran in exchange for Tehran giving up its nuclear weapons program.

Iranian President Hassan Rouhani sits among senior army staff as he delivers his speech during the annual military parade marking the anniversary of the outbreak of its devastating 1980-1988 war with Iraq, on September 22, 2017 in Tehran.

Iranian President Hassan Rouhani, who says Iran's nuclear program has always been designed for peaceful energy purposes, has said that the U.S. walking away would damage international trust of the U.S.

"Every word was analyzed many times by countries involved before its ratification," Rouhani told NBC News in September, "so if the United States were to not adhere to the commitments and trample upon this agreement, this will mean that it will carry with it the lack of subsequent trust from countries towards the United States."

And allies fear that killing the agreement could prompt Iran to resume its nuclear weapons program, perhaps triggering a nuclear arms race throughout the Middle East.

Trump aides said their approach to the Iran nuclear deal is part of an overall strategy designed to confront the Tehran government over what they call its bad behavior, including support for terrorism and efforts to destabilize other countries.

While the nuclear agreement is flawed in the administration's view, Tillerson said it is "only one part of what concerns us" about Iran.

De-certification would not kill the deal outright; that would be up to Congress.

Lawmakers have three options, Tillerson said: Do nothing and refuse to slap new sanctions on Iran, thereby keeping the existing deal alive; re-impose economic sanctions, effectively killing the agreement; or push for new negotiations for additions that Trump believes will "put more teeth" in the demands on Iran.

One possible provision would be adding "trigger points," new rules that would lead to an immediate re-imposition of sanctions if Iran violates them. One example, Tillerson said, would be development of prohibited ballistic missiles.

Some U.S. officials also want to eliminate "sunset provisions" in the existing agreement, which allow Iran to resume its nuclear program after a decade or more.

It is not clear whether U.S. allies or Iran would be willing to engage in new talks, much less a new agreement.

Trump's speech at the White House, scheduled for 12:45 p.m, precedes a Sunday deadline to tell Congress whether or not it will certify the agreement.

Trump has signaled his de-certification move for months, siding with critics who say the 2015 agreement gives Iran too much room to cheat, even as they profit from the elimination of economic sanctions.

"I think it was one of the most incompetently drawn deals I've ever seen," Trump told Sean Hannity in an interview taped Wednesday. "We got nothing, we got nothing. They got a path to nuclear weapons very quickly."

Despite similar attacks on the agreement, Trump has agreed to re-certify twice already this year, drawing criticism from some supporters who are also suspicious of Iran's intentions.

Tillerson pointed out that Trump, while attacking the agreement, has also said he would be willing to see it strengthened.

In his speech on Friday, Trump is expected to ask Congress to change the law requiring him to make a certification statement to Congress every 90 days.

White House spokeswoman Sarah Sanders said it is only one part of an overall strategy "to deal with all of the problems of Iran being a bad actor."

Since before taking office in January, Trump and his aides have criticized Iran's ballistic missile program, as well as what they call its support for terrorism and efforts to de-stabilize other Middle Eastern countries, including Iraq, Yemen, and Syria.

They have also cited Iranian threats toward Israel, a notably vocal opponent of the nuclear agreement.

Supporters note that inspection organizations have said Iran is in compliance with the demands of the existing agreement.

Trump and aides have said that Iran may be living up to the letter of the agreement — "we don't dispute that they are under technical compliance," Tillerson said — but argued that the deal overall is flawed and Iran's de-stabilizing activity in the region undermines the spirit of the agreement.

Tillerson and National Security Adviser H.R. McMaster said they have discussed their new Iran approach with members of Congress. While a new agreement may not be possible, they said some lawmakers have been receptive, and improving the agreement is worth a try in any case.

Said McMaster: "Nobody's for Iran getting nuclear weapons."