UPDATE 1-Microsoft delays office reopening date indefinitely in United States

(Adds company comment, background)

Sept 9 (Reuters) - Microsoft Corp on Thursday decided to push the dates for the full reopening of its offices in the United States indefinitely due to the highly contagious Delta variant.

"Given the uncertainty of COVID-19, we've decided against attempting to forecast a new date for a full reopening of our U.S. work sites in favor of opening U.S. work sites as soon as we're able to do so safely based on public health guidance," Microsoft said in a blog post.

Microsoft had earlier said it will open its Redmond headquarter as well as other U.S. offices on Oct. 4.

Some big tech firms are delaying a return to office, while others like Apple and Facebook Inc are making vaccinations mandatory due to the spike in COVID-19 cases in the country.

The software giant said it will also give a 30-day transition period that provides time for employees to prepare before getting back to offices. (Reporting by Tiyashi Datta in Bengaluru; Editing by Arun Koyyur)