OpenTable is getting into the food delivery business.

The world's biggest online restaurant reservation service has been watching warily as more diners opt for delivery. So the San Francisco-based company decided to partner with Caviar, GrubHub and Uber Eats to offer delivery through its app.

When OpenTable's updated site launches this week, it will give diners a delivery option for 8,000 restaurants in 90 U.S. cities. If they select delivery, users will be directed to the restaurant's preferred service to complete the transaction.

OpenTable says it decided to add a delivery option about nine months ago but didn't want to operate its own fleet. Delivery companies will pay OpenTable a small fee for any customers that come to them through its app.