President Donald Trump’s possible withdrawal from the Iran nuclear deal could dissuade other nations from entering agreements with the U.S., European Union foreign policy chief Federica Mogherini said on Wednesday.

“The message that America would send to the rest of the world is that America cannot be trusted upon, because a deal that America voted for just two years ago in the U.N. Security Council with a resolution unanimously adopted, a deal that America helped to shape enormously, enormously, would be rejected by the same country,” Mogherini told PBS NewsHour anchor Judy Woodruff on Wednesday from EU headquarters in Brussels.

It would also indicate that the United States would be willing to renegotiate agreements with every new administration, giving other countries reason to hesitate on negotiations if they felt future leadership would give them a better deal, Mogherini added.

“This is not a way of making deals, not in foreign policy, not in private businesses, and I think President Trump understands this perfectly well,” Mogherini said.

Mr. Trump has until Sunday to decide whether to recertify that Iran is in compliance with the Obama-era nuclear agreement, which limits Iran’s nuclear program. He also must decide whether the deal is still in the national interest of the U.S. Trump said Wednesday he will announce his decision “very soon,” without specifying what that decision is or when it would come. Several media outlets have pointed to White House sources who expect the president to decertify Iran’s compliance with the deal, which Trump has called “catastrophic” for the U.S., Israel and the Middle East. If he does refuse to certify, Congress would have 60 days to decide whether to renew sanctions lifted in exchange for Iranian nuclear compliance.

READ MORE: Trump may scrap the Iran nuclear agreement. Here’s what you need to know

After a meeting in September, Mogherini, who helped broker the 2015 pact, pointed out that all of the countries who signed the deal — including the United States — have found Iran is in compliance with the agreement. Secretary of State Rex Tillerson and U.S. Ambassador to the U.N. Nikki Haley have said the U.S. interprets the 2015 agreement differently than the other countries involved.

In a Tuesday phone call with British Prime Minister Theresa May, Trump expressed the need to work together “to hold the Iranian regime accountable for its malign and destabilizing activities, especially its sponsorship of terrorism and its development of threatening missiles,” according to the White House.

READ MORE: Deal to keep Iran from making a nuclear bomb in 10 points

British Foreign Secretary Boris Johnson, who spoke with Tillerson the same day, said that “while Iran’s destabilizing activities in the region are unacceptable, the regime has upheld its nuclear commitments,” according to a statement released from his office.

House Foreign Affairs Committee Chairman Ed Royce, R-Calif., who held a hearing on Iranian threats on Wednesday, called the deal a failed “gamble” that Iran would become a responsible actor. However, “as flawed as the deal is, I believe we must now enforce the hell out of it,” and make sure inspectors have better access to possible nuclear sites, he said.

Watch Mogherini’s full interview with the NewsHour’s Judy Woodruff on Wednesday’s broadcast.