TOKYO (Kyodo) -- U.S. authorities extended a deadline imposed on Japan's Nippon Steel Corp. and United States Steel Corp. to abandon their merger plan to June 18, the companies said Sunday, a move that came as they fight to advance the deal in courts.

U.S. President Joe Biden issued an order on Jan. 3 to block the $14.1 billion takeover of U.S. Steel by the Japanese company on national security grounds and urged the companies to take all steps necessary to "fully and permanently" abandon the deal within 30 days.

However, the order also stated the period can be extended by the Committee on Foreign Investment in the United States, a panel of U.S. federal agencies involved in screening the proposal.

The extension of the Feb. 2 deadline followed a request from Nippon Steel.

"We are pleased that CFIUS has granted an extension to June 18," U.S. Steel said in a statement. "We look forward to completing the transaction, which secures the best future for the American steel industry and all our stakeholders."

Reacting to Biden's order, Japan's biggest steelmaker and U.S. Steel, the third-largest U.S. producer, have filed two federal lawsuits in the United States seeking to protect their merger plan from what they called "illegal and improper political and anticompetitive interference."

One of the lawsuits asks a court to "set aside the unlawful CFIUS review process and President Biden's accompanying order" and to instruct CFIUS to reassess the proposal.

The acquisition plan was announced in December 2023. U.S. Steel was once a symbol of American economic prowess, but it has struggled to compete with foreign rivals.

The deal became a hot-button issue in the 2024 U.S. presidential election, as Pennsylvania, where U.S. Steel is headquartered, is a key battleground state. The leadership of the politically influential United Steelworkers union also came out against the takeover.

During the election campaign, Biden, who leaves office on Jan. 20, Democratic presidential candidate Vice President Kamala Harris and Republican President-elect Donald Trump all publicly opposed the deal.