AT&T Inc said on Friday it would record a $1 billion non-cash charge for the current quarter related to the new U.S. health care reform law signed by President Barack Obama this week.

AT&T's charge appeared to be the largest in a series of charges announced by U.S. companies this week.

The operator, whose annual revenue is expected to be $124.1 billion this year, said the charge is the result of a provision in the law related to the tax treatment of Medicare subsidies.

As a result of the legislation, the company, which ended 2009 with 282,000 employees, said it will be evaluating prospective changes to the health care benefits it offers to employees at retirees.

Under the health care overhaul large ranks of retirees can no longer deduct from their taxes the subsidies paid by the federal government for retiree drug benefits.

AT&T, the biggest U.S. telephone company, declined to comment beyond its statement filed with the U.S. Securities and Exchange Commission when asked whether the new law would create any more changes beyond the first quarter.

According to reports, Verizon Communications , the second biggest U.S. phone company, told employees that tax burdens under the new law would likely filter down to employees. Verizon declined to comment.

Other companies that announced health care reform related charges include Deere , a maker of farm equipment, which sees a $150 million charge for its current quarter, and Caterpillar , which warned of a $100 million charge.

AT&T shares rose 9 cents to close at $26.24 on the New York Stock Exchange.

(Reporting by Sinead Carew; Editing by Leslie Gevirtz and Richard Chang)