United Airlines is near an agreement to purchase a double-digit number of Airbus A321 narrowbody jets, Bloomberg News reported on Tuesday, citing people familiar with the matter.

An order may be announced as soon as Tuesday, adding to the 120 A321s United Airlines already has on backlog with Airbus, according to the report.

Airbus declined to comment, while United Airlines did not immediately respond to a Reuters request for comment.

Both Airbus and rival Boeing have laid out ambitious ramp-up goals as air travel and aircraft sales rebound, with Airbus producing in-demand single aisle planes even faster than the U.S. planemaker.

Last year, United Airlines unveiled a huge order of 100 Boeing 787 Dreamliners and 100 737 MAXs to grow post the pandemic and replace older, less-efficient aircraft.

At that time, the order had sparked concerns about United Airlines' balance sheet. The company has said it expects to take delivery of about 700 jets by 2032, the cost of which may reach $50 billion, according to brokerage Jefferies.

The rush to order jets comes amid a boom in travel demand and when airlines are facing increasing pressure to cut emissions.

Some analysts have said new aircraft shortages due to a broken supply chain have spooked airlines into placing large orders for jets.

(Reporting by Mehr Bedi in Bengaluru; Additional reporting by Tim Hepher; Editing by Shounak Dasgupta)