Shares of Sprint fell sharply Monday after a news report said its parent SoftBank had called off talks with T-Mobile about a possible merger of the two wireless companies.

Sprint (S) stock lost 11% before closing down 9% at $6.34. T-Mobile (TMUS) shares fell 5%.

According to the Nikkei Asian Review, Japan's SoftBank ended its effort to become a larger player in the U.S. wireless market after Sprint and T-Mobile were unable to agree on how ownership of the new company would be structured. SoftBank acquired Sprint in 2013.

Nikkei reported that SoftBank planned to contact T-Mobile-owner Deutsche Telekom as early as Tuesday about ending negotiations. Representatives from SoftBank and T-Mobile did not respond to a request for comment.

The pairing of T-Mobile, which has about 70 million subscribers, and Sprint, with its nearly 54 million, would create a bigger competitor to industry leaders AT&T, which has 135.7 million and Verizon, with 114.5 million.

In 2014, the nation's No. 3 and No. 4 wireless providers considered joining forces but eventually called off merger talks because it was believed the U.S. regulatory hurdles under the Obama administration were too steep.

In December, SoftBank CEO Masayoshi Son met at Trump Tower with then-President-elect Donald Trump, rekindling speculation that SoftBank would renew merger efforts under a Republican administration.

SoftBank Group said it would invest $50 billion into the U.S. economy and add 50,000 jobs.

Son reportedly also sought a merger of Sprint and Charter Communications earlier this year, but Charter rebuffed that in July.