U.K. rail and coach ticket booking platform Trainline.com Ltd. is planning to launch a £1 billion IPO in London as soon as the summer, Sky News reported, citing people familiar with the matter.

The news outlet said an IPO became KKR & Co.'s preferred exit option for Trainline after a series of bids from other private investors.

KKR was looking to add more investment banks to join JP Morgan and Morgan Stanley on the listing, the sources said, adding that the timing of the IPO will depend on U.K. market conditions after the country's exit from the EU.

KKR could still pursue a private sale of its portfolio company should a bidder's offer price reflect Trainline's growth prospects, the people said. KKR acquired Trainline in 2015 from an investor group that included Exponent Private Equity LLP.

"We have no fixed sale plans at this time," a Trainline spokeswoman said, according to Sky News.