On Assignment Inc. said that it is buying Valesta, a Belgium provider of specialized staffing in clinical research, for about $17.6 million.

The Calabasas health care staffing company said late Wednesday that the acquisition will increase its international presence and ability to staff workers in the life sciences sector. The company expects the acquisition will boost per-share earnings this year.

“We are focused on our organic and acquisition growth strategy to reach $1 billion in revenue over the next five years,” said Chief Executive Peter Dameris in a statement. “The acquisition of Valesta positions us well to reach our 2011 acquired revenue goals.”

Valesta is based in Mechelen, Belgium and has offices in Spain and the Netherlands. The deal gives its owners, who will continue to operate the company, the opportunity to earn an additional $7.1 million over three years if certain milestones are reached.

On Assignment plans to use cash and its senior credit facility to finance the deal, which is expected to close on Monday.

Shares were up 3 cents, or less than 1 percent, to $10.02 in midday trading on the Nasdaq.