Instacart, whose business has skyrocketed during the pandemic, has partnered with Walmart for same-day deliveries in several U.S. cities.

The development comes on the heels of Uber's integration with grocery delivery company Cornershop, and also marks a stepping up of the competition with one of Walmart's biggest rivals: Amazon.

Instacart confirmed on Tuesday that it will offer a same-day delivery option at Walmart locations in four markets -- Los Angeles, San Francisco, San Diego and Tulsa.

"The new partnership brings thousands of items - from groceries, alcohol and pantry staples to home decor and improvement, personal care, electronics and more - at everyday low prices from Walmart stores to customers' doors in as fast as an hour," said an Instacart spokesperson in a statement to CNN Business.

After years of working to build momentum, Instacart and other food delivery services have found their moment during the pandemic. Since March, Instacart has added hundreds of thousands of new contract workers -- who shop and deliver groceries -- and raised $325 million in new financing, giving it a valuation of nearly $14 billion.