GlaxoSmithKline ( GSK) said Wednesday that its long-running, multibillion-dollar tax dispute with the Internal Revenue Service just got bigger. The U.K.-based drug giant said it had received a claim from the IRS alleging that $1.9 billion is owed for the years 1997-2000 for profits from Glaxo Wellcome, which merged with SmithKline Beecham to form GlaxoSmithKline in 2000. The company is contesting the claim; if it loses, however, it could be assessed an extra $700 million in interest. The IRS action isn't a surprise. Twelve months ago, GlaxoSmithKline said it expected to receive such a claim for 1997-2000 because the company already had been assessed a $2.7 billion tax bill from the IRS for 1989 through 1996. Interest payments for this period could run as high as $2.5 billion. "The company continues to believe ... that it has made adequate provision for tax liabilities which could arise from these tax assessments," GlaxoSmithKline said Wednesday. The company said it tried unsuccessfully to settle the dispute by asking U.S. and U.K. tax officials to negotiate the matter. Instead, the company now says it will consolidate the 1997-2000 tax dispute with a lawsuit involving the 1989-1996 dispute pending in the U.S. Tax Court. A trial date has been set tentatively for October 2006. The tax dispute didn't appear to bother investors. GlaxoSmithKline stock was up 40 cents, or 0.9%, to $45.10.