Nippon Steel said it wouldn't be deterred by Biden’s decision last week to block its $15 billion bid for the storied U.S. steelmaker.

We have written extensively about the president's decision, the political dynamics at play and possible scenarios for the future. Now that Nippon Steel has taken the unprecedented step of suing the government of Japan's most important ally, the saga appears to be far from over, and there will be a lot more to write about.

U.S. Steel and its would-be Japanese suitor filed twin lawsuits Monday to defend their $15 billion merger. President Biden issued an order on Friday to block the deal, citing national security concerns.

U.S. President Joe Biden’s decision to reject a bid by Nippon Steel to acquire U.S. Steel on national security grounds isn’t the first time friction over trade and investment has irked Washington’s closest ally in Asia.

The Japanese firm’s planned purchase of its U.S. rival was blocked last week by President Joe Biden after a year of diplomatic tension, political debate and lobbying efforts from the companies and unions. Biden, who had previously said he opposed the tie-up, cited national-security risks, despite Japan being a close ally.

President Biden has blocked a deal between U.S. Steel and Japan's Nippon Steel that could impact the relationship with the American ally and have global economic repercussions. CBS News' Nicole Sganga has more.

Stock via Getty Images Having a 123-year-old iconic American steel giant be taken over by a Japanese producer has not gone well in the US of A.

The companies condemned the president's decision and hinted at taking legal action, while U.S. Steel's CEO accused Biden of "political corruption."

TOKYO -- Nippon Steel's plan to buy U.S. Steel has entered a new phase with the companies' declaration of a full-scale legal war against the U.S. government. They hope the lawsuits will overturn President Joe Biden's order to give up the acquisition.

Let’s have faith that Trump will reject the Biden administration’s politically motivated interference in the deal or get an even bigger, more spectacular one.

Logical, but not perfect. The Wall Street Journal pointed out that a Cliffs-U.S. Steel combination "would control 100% of U.S. blast furnace production, 100% of domestic steel used in electric-vehicle motors, and 65% to 90% of other domestic steel used in vehicles."