By Tamara Mathias and Michael Erman

(Reuters) - U.S. drugmaker AbbVie Inc (ABBV.N) on Friday lowered its forecast for overseas sales of its top-selling medicine, Humira, due to larger-than-expected pricing cuts because of new competition in Europe.

"We've seen discounting at ranges from as low as 10 percent to as high as around 80 percent," Chief Executive Officer Richard Gonzalez said on a conference call with analysts.

"The discounting has been on the higher end of the planning scenarios that we had laid out."

The highest discounting was seen in Nordic countries, Gonzalez said, adding that the company believes discounting would likely "moderate" going forward.

However analysts expect competition from cheaper biosimilar versions of the medicine to remain intense beyond next year in Europe.

"We do not have evidence from prior European Union biosimilar launch dynamics that the pace of discounting will slow in the second year of availability," Leerink analyst Geoffrey Porges said. "We would expect erosion to intensify in 2020, not slow."Mylan NV (MYL.O), Biogen Inc (BIIB.O) Amgen Inc (AMGN.O) and Novartis AG (NOVN.S) have all begun selling biosimilar versions of Humira in Europe, fueling investor concerns as the world's top-selling prescription medicine accounts for about two-thirds of AbbVie revenue.

AbbVie is not expected to face biosimilar competition in the United States until 2023.

Outside the United States, the company expects Humira sales to drop around 26 to 27 percent next year, above its previous forecast of 18 to 20 percent. It projected international sales of the drug for rheumatoid arthritis and other autoimmune disorders to approach $6.3 billion in 2018.

Total Humira sales for the quarter rose 9 percent to $5.12 billion.

Gonzalez was bullish about AbbVie's portfolio of cancer treatments and said he was confident of delivering double-digit earnings growth in 2019, despite the Humira biosimilar threat and expected higher spending to launch new drugs.

The company also increased its quarterly dividend by about 11 percent.

"The fundamental concerns about AbbVie are about long-term growth prospects. The dividend increase will make AbbVie appear more attractive, but it's not enough," BMO Capital Markets analyst Alex Arfaei said in a note.

AbbVie shares were flat at $79.77, shedding some early gains following the company's Humira comments. They had climbed as much as 5 percent after the company reported higher-than-expected third-quarter earnings.

Results in the quarter were buoyed by higher-than-expected sales of leukemia drug Imbruvica, which AbbVie shares with Johnson & Johnson (JNJ.N). It had sales of $972 million, while analysts had been estimating about $885.6 million.

AbbVie also raised its 2018 adjusted earnings forecast to between $7.90 and $7.92 per share from a prior range of $7.76 to $7.86. Analysts had forecast $7.88 per share.

Excluding items, AbbVie earned $2.14 per share, topping analysts' average forecast by 12 cents, according to data from Refinitiv IBES.

In the quarter, the company benefited from a lower adjusted tax rate of 9.1 percent, compared with 19 percent last year.

(Reporting by Tamara Mathias in Bengaluru and Michael Erman in New York; editing by Sriraj Kalluvila and Bill Berkrot)