Amgen Inc issued a 2010 forecast on Monday that showed potential to exceed Wall Street expectations, but the company's slightly higher fourth-quarter profit came in shy of analyst estimates primarily due to higher expenses.

The world's largest biotechnology company, which has been struggling with falling sales of its once top-selling anemia drug Aranesp, said it expects 2010 revenue between $15.1 billion and $15.5 billion and earnings of $5.05 to $5.25 per share, excluding items.

Wall Street analysts on average expect 2010 revenue of $15.31 billion and earnings of $5.13 per share, which is below the midpoint of Amgen's forecast range.

Amgen said it expects a return to top-line growth this year and still expects 2010 U.S. approval of the experimental osteoporosis drug denosumab, which is widely considered the company's most important future growth driver.

Sanford Bernstein analyst Geoffrey Porges called the 2010 forecast surprisingly strong and said it is better than I expected.

Eric Schmidt, an analyst for Cowen and Co, was also pleased with the forecast.

I think the guidance, for a company that gives conservative guidance and faces some unknowns in 2010, was solid, Schmidt said.

Amgen said fourth-quarter net profit rose to $931 million, or 92 cents per share, from $925 million, or 87 cents per share, a year ago.

Excluding items, Thousand Oaks, California-based Amgen earned $1.05 per share. That was 7 cents short of analysts' expectations, according to Thomson Reuters I/B/E/S.

Revenue for the quarter rose 2 percent to $3.8 billion.

The revenue in Q4 was surprisingly strong, with a big surge in R&D (research and development expenses) dragging down the EPS number, Porges said.

Amgen said it has provided the U.S. Food and Drug Administration with all the information the agency had said it needs before it can approve denosumab to treat and prevent osteoporosis in post-menopausal women.

The company said in October that the FDA delayed approval of the drug, which would be sold under the brand name Prolia, pending receipt of certain items -- including information about a program to monitor the drug once on the market.

Cowen's Schmidt said he expects the FDA to conduct a six-month review of the Prolia resubmission.

Everything we know about the FDA says they will take their time. A six-month clock takes us to sometime in July. Hopefully sometime in the third quarter this thing gets approved, Schmidt said.

Meanwhile, Amgen expects important data this quarter on denosumab's ability to prevent skeletal fractures in prostate cancer patients, and aims to seek approval of the drug later this year to treat fractures in advanced cancer patients.

The important thing is we expect approval and we are ready, Chief Executive Kevin Sharer told analysts and investors on a conference call.

The company said it has already hired its primary care sales force for the drug, which added to expenses for the quarter. It also cautioned that 2010 sales and marketing expenses would increase with the launch of Prolia.

Fourth-quarter sales of Aranesp, which have been hit by safety concerns and reimbursement restrictions, fell 8 percent to $648 million, shy of Wall Street estimates of about $680 million. U.S. sales were down 20 percent.

Sales of its older anemia drug Epogen, however, have clearly headed back in the right direction with an increase of 9 percent to $703 million for the quarter. That easily topped expectations of between $658 million and $667 million.

Sales of the widely used rheumatoid arthritis drug Enbrel were flat at $912 million, and well shy of analyst estimates of about $933 million and the previous quarter's $924 million.

Combined worldwide sales of the white blood cell boosters Neupogen and Neulasta rose 2 percent to $1.20 billion, in line with expectations.

Amgen shares were up half a percent at $56 in after-hours trading after closing at $55.71 on the Nasdaq.

(Additional reporting by Deena Beasley in Las Vegas and Ransdell Pierson in New York; editing by Robert MacMillan, Matthew Lewis and Steve Orlofsky)