The Romanian, 26, will be replaced in the Connecticut Open by Switzerland's Belinda Bencic.

Halep won the Rogers Cup in Montreal and reached the Cincinnati Masters final in the past two weeks.

"I feel very sore and I need some rest. I had so many matches in the last two weeks, so it's tough," she said.

The US Open at Flushing Meadows in New York starts on 27 August.

Halep's best run in the tournament came in 2015 when, seeded second, she suffered a shock defeat by Flavia Pennetta in the semi-finals.