Gannett Co., the owner of USA Today, has agreed to pay $1.8 billion for the 73 percent of auto-sales website Cars.com it doesn’t already own, according to a person familiar with the matter.

Gannett, which already owns about 27 percent of Cars.com, values the whole business at about $2.5 billion, the person said, asking not to be identified discussing private information. The deal could be announced as soon as Tuesday, the person said.

Jeremy Gaines, a spokesman for Gannett, declined to comment. A representative for Classified Ventures, the entity that owns Cars.com, couldn’t immediately be reached to comment.

Cars.com, which was started in 1998, lets user check prices, compare models and read reviews of auto dealers. Classified Ventures is backed by four newspaper publishers in addition to Gannett: McClatchy Co., Tribune Co., AH Belo Corp. and Graham Holdings Co.