Amgen, the world's largest biotechnology company, on Thursday raised its 2013 earnings forecast to account for a Puerto Rico excise tax credit due to federal settlements for prior years.

Amgen, which has a manufacturing facility in Puerto Rico, said that it now expects adjusted 2013 earnings of $7.05 per share to $7.35 per share, and that it would record the credit in the first quarter. The company last month had forecast earnings per share of $6.85 to $7.15.

The 2013 revenue forecast remains unchanged at $17.8 billion to $18.2 billion.

Amgen made the announcement in conjunction with a meeting in New York with analysts and investors at which management was providing an update of its business strategy, including details on its pipeline of drugs in development and plans to manufacture generic versions of biotech drugs, known as biosimilars.

Amgen Chief Executive Robert Bradway said the company plans to launch six biosimilars in 2017 - four cancer drugs and two for inflammatory diseases.