President Donald Trump's decision on the 2015 Iran nuclear deal could come on Friday, and experts say the "writing is on the wall" that the administration won't recertify the landmark agreement and he likely will turn his attention to getting European support on fixing it.

NBC News reported the White House briefed lawmakers Wednesday on the pending decision and those who left were convinced the Obama-era nuclear deal would get decertified. It also reported the announcement would probably be Friday and that the administration doesn't want to scrap the deal entirely and proposed a legislative remedy.

Even so, some experts told CNBC that decertification will undermine the international deal and encourage hardliners in Tehran to push for nuclear weapons. Also, they said nixing certification of the Iran deal and trying to renegotiate it will discourage North Korea from ever considering a denuclearization accord.

"What Trump is doing is opening a very unnecessary 'Pandora's box' of troubles at a time when he is unable to competently handle the crisis with North Korea's nuclear program," said Daryl Kimball, executive director of the Arms Control Association, which supports the Iran deal.

Trump, who has been sharply critical of Iran and accused Tehran of working with North Korea on lethal weapons, faces an Oct. 15 deadline on whether to certify to Congress that Iran is compliance with the terms of the nuclear agreement.

"I expect President Trump will not certify it," said Elizabeth Rosenberg, an Iran expert at the Center for a New American Security, a progressive think tank. "He's been quite clear for a long time that it's not his plan to certify it."

If Trump does decertify the accord as expected, it would put him at odds with Defense Secretary James Mattis, who last week said Tehran was "fundamentally" in compliance with the agreement and that the U.S. should stick with the pact.

Rosenberg said decertification would effectively open a 60-day window for Congress to consider sanctions on Iran. However, some members of Congress have expressed a willingness to hold off on sanctions to give Trump time to negotiate a strategy with the Europeans to alter the deal.

Several European allies have urged Trump not to nix the agreement, but instead to build on it, possibly addressing "sunset" provisions (by 2026, key nuclear restrictions lift on the accord).

"The decertification is an essential first step to persuading the Europeans that the alternatives to fixing the deal could be President Trump's decision to abandon the deal," said Mark Dubowitz, CEO of the Foundation for Defense of Democracies, a nonpartisan policy institute.

Yet Iran's semi-official Fars News Agency reported Wednesday that the country's foreign minister said Tehran "will never" renegotiate the deal.

On the other hand, some argue decertification and the possibility of U.S. sanctions on Iran might win support from the Europeans. Besides, Tehran might see things differently with the threat of sanctions.