Google said Wednesday it was adding fresh foods to its grocery delivery service, ramping up its challenge to Amazon and a long list of delivery startups.

The US online giant said its Google Express service -- which launched in 2013 by offering non-perishable goods -- would include a range of fresh items in test markets in the Los Angeles and San Francisco areas.

"Everyone wants milk delivered with their cookies -- that's why we're excited to start adding fresh groceries to Google Express," said product manager Prabhu Balasubramanian.

He said consumers liked the service but that "we've also heard your feedback that you'd love for Express to help you check off your entire grocery list, including fruit, vegetables, meat, seafood, dairy, and frozen foods."

"Whether you need to restock your pantry, get some ingredients for tonight's dinner, or just need some help carrying the heavier stuff -- all you have to do is place your order, and we'll take care of the rest," he said in a blog post.

Google Express, which is offered in a handful of US cities, takes a delivery charge of $3 for members and $5 for non-members.

Google has ramped up the service as Amazon has expanded its grocery delivery program to include fresh items.

Both online giants are competing against a wave of startups in the US and around the world that offer fast grocery delivery, with the help of mobile applications.