American Airlines said on Friday that it was not interested in a merger with United Airlines and had not held any such talks, diminishing prospects of an industry-reshaping deal that would face tough regulatory scrutiny.

A combination of two of the largest U.S. network carriers would mark the biggest consolidation move in more than a decade, further tightening a domestic market already dominated by four similarly sized players.

It would invite extraordinary scrutiny from regulators, labor unions and consumer advocates, all wary of higher fares ‌and reduced competition.

United Airlines CEO Scott Kirby pitched the ​potential for merging with American Airlines in a meeting with U.S. President Donald Trump in late February, Reuters reported on Monday.

The meeting with Trump was three days before the start of the U.S.-Israeli war with Iran that sent jet fuel prices soaring and has led ​airlines to raise fares and fees to offset higher costs.

“While changes in the broader airline marketplace may be necessary, a combination with United would be negative for competition and for consumers, and therefore inconsistent with our understanding of the (Trump) Administration’s philosophy toward the industry and principles of antitrust law,” American Airlines said in a statement.

United Airlines and the White House did not immediately respond to requests for comment.

The White House has previously said it has no opinion on a potential United Airlines deal for American Airlines.

(Reporting by Megavarshini G. Somasundaram in Bengaluru; Editing by Pooja Desai)