President Donald Trump announced Tuesday he will withdraw the U.S. from a nuclear pact with Iran, a move that threatens Boeing's multibillion dollar deals to help restock Iran's aging commercial air fleet.

The world's largest aerospace company has agreements to sell planes worth roughly $20 billion to Iranian airlines, based on list prices. The number of aircraft in the agreements is tiny compared with Boeing's total order book, however. Boeing ended the first quarter of this year with a backlog of more than 5,800 airplanes, including more than 4,600 orders for 737s.

Boeing said it had not included the Iranian deals in its order book, so its backlog remains unchanged. Boeing's European rival Airbus, however, has included its deals with Iranian airlines in its order book.

"Following today's announcement, we will consult with the U.S. government on next steps," Boeing said in a statement.

Shares of Boeing ended the day down 0.6 percent.

Trump said Tuesday he would restore sanctions on Iran. The 2015 pact lifted sanctions, after Iran agreed to limits on its nuclear program, allowing the deals with Iranian airlines to take place.

Boeing announced the largest of its deals with Iranian airlines in December 2016: 80 jets for Iran Air – including 50 of the 737 MAX 8 model. In April 2017, Iran Aseman Airlines signed an agreement to purchase 30 Boeing 737 MAX planes, with an option to buy 30 more.

When it announced the Iran Air deal, Boeing said such an order would support 100,000 U.S. jobs. That same month, Boeing's rival Airbus announced a deal to sell 100 planes to Iran Air. A list of Airbus' orders through the end of April included more than 100 planes on order for Iran Air and Iran Aseman Airlines. Airbus did not immediately respond to a request for comment."

If the aircraft agreements are scrapped outright, it won't likely have a big impact on Boeing because of the company's large backlog of jets, particularly for narrowbody 737 aircraft, said Richard Aboulafia, vice president at Teal Group.

"Would have been nice to get but far from a major impact," Aboulafia said.

The company's current 777 production rate "is not dependent on the Iranian orders," CEO Dennis Muilenburg said on an earnings call last month. The 2016 Iran Air agreement with Boeing included 15 widebody 777-9 and 15 777-300ER models. Boeing had more than 400 orders for its widebody 777 at the end of March.