Investing.com -- United Airlines Holdings Inc. CEO Scott Kirby suggested Tuesday that acquiring a smaller airline may not be worthwhile, citing the significant effort required for such a transaction.

"Doing a merger takes a lot of calories and a lot of energy," Kirby said in an interview with the New York Times. "The hurdle is a whole lot higher for a small airline than it is for a big airline, for me."

The remarks follow Kirby's statement earlier this week outlining reasons for a potential combination between United and American Airlines Group Inc. Bloomberg News reported earlier this month that Kirby pitched the merger to President Donald Trump.

The proposal has faced opposition from the industry and was rejected by American CEO Robert Isom.

The discussion has sparked speculation about other potential deals, including with JetBlue Airways Corp. Kirby declined to comment on speculation about a possible JetBlue deal.

United and JetBlue currently have a partnership that gives United access to some gates at John F. Kennedy International Airport. United operates from Newark as its New York City area hub.

JetBlue carries approximately $9 billion in total debt and has required additional borrowing to maintain liquidity. Analysts project another loss for the carrier this year.

Kirby has maintained his focus on what he called a "big, bold vision" with American, stating the combination would expand capacity, create jobs and deliver value to travelers.