UPDATE 1-US says Novartis' Gleevec websites misleading

* FDA releases April 21 letter to Novartis

* Websites promoted unapproved use - FDA

WASHINGTON May 4 (Reuters) - Two Novartis AG (NOVN.VX) (NVS.N) websites made misleading claims about the company's Gleevec cancer drug, U.S. regulators said in a letter released on Tuesday.

"These websites are false and misleading because they promote the drug for an unapproved use, fail to disclose the risks associated with the use of Gleevec and make unsubstantiated dosing claims," the Food and Drug Administration said in an April 21 letter.

The Novartis-sponsored websites are www.gistalliance.com and www.cmlalliance.com, the FDA letter said.