Belgian drugmaker UCB forecast revenue and profit would fall this year as generic competition was expected to halve European sales of its top-selling drug.

The company, which specializes in diseases of the immune and central nervous systems, is in a transition phase as it faces generic competition for epilepsy blockbuster Keppra and seeks to drive sales of three main new drugs.

UCB forecast 2012 revenue would drop to 3.1 billion euros after rising 1 percent to 3.25 billion euros in 2011 and recurring core profit would decrease to between 630-660 million euros ($840-$880 million).

We now know that more than 100 companies have generic approval across Europe, and so we have to expect that this will cause a decline of the Keppra business in Europe, a UCB spokeswoman told Reuters by telephone.

We do expect that in the first 12 months, which means 2012, the European Keppra business will decrease by 50 percent, she said.

In 2011, UCB managed to increase global sales of Keppra by 3 percent despite the fact that its period of market exclusivity had expired, as competitors took longer than expected to get generic products off the ground in Europe.

Last year, UCB's core profit fell 7 percent to 683 million euros after the cost of launching new medicines and higher drug trial expenses pushed down 2011 earnings.

That missed an average of 696 million euros expected by 12 banks and brokers polled by Reuters.

Sales of its newer products -- epilepsy drug Vimpat, Neupro for Parkinson's disease, and Cimzia to treat bowel disorder Crohn's disease -- came in broadly in line.

UCB increased its dividend by 2 percent to 1.00 euros, slightly less than 1.01 euros per share predicted in the Reuters poll. ($1 = 0.7501 euros)

(Reporting by Ben Deighton; Editing by Jon Loades-Carter and Philip Blenkinsop)