The Committee on Foreign Investment in the United States panel, which has been reviewing the proposed takeover for much of this year, must refer its decision to Biden by Dec. 22 or 23, said the people, who asked to not to be identified discussing a confidential process.

It’s not clear exactly what the CFIUS review will say. However, any referral to the president suggests at least one member of the panel sees the deal posing a risk. Nippon Steel and U.S. Steel are poised to pursue litigation over the process if Biden decides to block the merger, some of the people said.

The fate of the once-fabled U.S. steelmaker has become a hot political issue since the company reached an agreement to be taken over by its Japanese suitor almost a year ago. U.S. Steel has said the deal represents a lifeline and warned it may move its headquarters out of Pennsylvania and shutter some operations if the merger collapses.

Biden—born in U.S. Steel’s home state of Pennsylvania—has long signaled opposition to the sale, and has said the company would remain domestically owned. At the same time, he has stopped short of a pledge to kill the deal, while President-Elect Donald Trump has promised repeatedly to block it.

“The President’s position since the beginning is that it is vital for U.S. Steel to be domestically owned and operated,” White House spokesperson Saloni Sharma said. “The CFIUS process was and remains ongoing.”

Shares of U.S. Steel tumbled as much as 22% and closed 9.7% lower at $35.26. “This transaction should be approved on its merits,” company spokeswoman Amanda Malkowski said. 

Nippon Steel shares rose as much as 1.2% shortly after the open on Wednesday before trading little changed as of 12:52 p.m. in Tokyo.

“It is inappropriate that politics continue to outweigh true national security interests—especially with the indispensable alliance between the U.S. and Japan as the important foundation,” Nippon Steel said in a statement. “Nippon Steel still has confidence in the justice and fairness of America and its legal system, and—if necessary—will work with U.S. Steel to consider and take all available measures to reach a fair conclusion.”

Japan’s Chief Cabinet Secretary Yoshimasa Hayashi declined to comment during a press conference on Wednesday, saying the government was aware of the report. 

Despite the political pressures swirling around the deal, Nippon Steel has worked for months to build support. The company announced separately on Tuesday a plan to offer a $5,000 bonus to every U.S. Steel worker if the takeover closes.

The CFIUS process was extended in September with a procedural maneuver. That pushed the referral deadline to this month and raised questions about whether the deal might proceed after the election, even as Biden dug in. “I haven’t changed my mind,” he said Sept. 27.

The powerful United Steelworkers union has also opposed the deal. Vice President Kamala Harris echoed Biden’s stance during her campaign as the Democratic nominee in the presidential election.

It’s unusual for CFIUS to reject acquisitions by entities based in a friendly nation such as Japan.

The exact timing of any announcement from Biden is unclear. The president has 15 days from the referral to announce a decision. Another extension to the CFIUS process—which would punt a decision to the next administration—isn’t expected, some of the people said.

Republican lawmakers last month called on Biden administration officials to preserve documents related to the sale, saying they were concerned the CFIUS process “has been subordinated to political interests.”