UPDATE 1-FDA won't OK Glaxo's experimental nausea drug

* Glaxo declines to comment on letter details

* Company reviewing FDA letter, says process ongoing

WASHINGTON, June 23 (Reuters) - The U.S. Food and Drug Administration said it will not approve GlaxoSmithKline Plc's (GSK.L) (GSK.N) experimental nauseau drug Rezonic for cancer or surgical patients, the drugmaker said on Tuesday.

The company said it received a "complete response" letter from the FDA, but offered no other information.

"A complete response letter is issued ... when the review of a file is completed and questions remain that preclude the approval of the application," the company said in a statement.

But a Glaxo spokeswoman said the review process was not over, but declined to give any details about the FDA's review.

"FDA did not reject our application -- rather they issued a complete response letter to indicate the application has been reviewed and specific, additional information is required for the product's approval. That essentially stops the review clock and allows a company to amend the application, then re-start the review process," she said.

The company said it would review the FDA's letter. Glaxo is seeking approval to market the drug for patients who experience nausea following surgery or chemotherapy treatments.

In May, the FDA canceled a public advisory meeting to discuss whether to recommend approval of the drug, known generically as casopitant. (Reporting by Susan Heavey; editing by Leslie Gevirtz)