Jan 12 (Reuters) - Quest Diagnostics said on Wednesday it was performing more than 100,000 COVID-19 tests a day, as the Omicron coronavirus variant drives a surge in testing demand in the United States.

"We saw a steep increase in our volumes in the fourth quarter, particularly the last two weeks in December, and it continues into January," Quest Diagnostics Chief Executive Officer Steve Rusckowski said at the annual J.P. Morgan Health Care conference.

The company said it performed over 120,000 PCR tests per day in the last couple of weeks of 2021, and over 150,000 tests a day at the beginning of this year. (Reporting by Amruta Khandekar; Editing by Shinjini Ganguli)