By Foo Yun Chee

AMSTERDAM (Reuters) - Dutch office goods supplier Corporate Express CXP.AS, a 2.5 billion euro ($3.9 billion) bid target of Staples Inc (SPLS.O: Quote, Profile, Research), posted a lower-than-expected rise in first-quarter organic sales at its Europe operations.

That makes it unlikely U.S. rival Staples will increase its unsolicited indicated offer of 7.25 euros per share, said analysts on Tuesday, even though organic sales growth at its North America operations met expectations.

Chief Executive Peter Ventress, speaking after an annual shareholders meeting held the same day, repeated that Staples' proposed offer "significantly undervalues the business."

"We're back on track to delivering this company to its full potential," Ventress told reporters.

Sales in Europe were up 3 percent, against 6 percent in the year-ago period and a 5 percent rise in the previous quarter. Analysts had expected underlying sales growth of 4-5 percent.

Organic sales growth in North America, which accounts for half its revenue, rose 2 percent after a 1 percent decline a year earlier and a 3 percent increase in the fourth quarter.

The company defines organic sales growth as excluding the effect of any possible acquisitions.

"These figures in themselves give little reason for Staples to raise its bid," said Rabo Securities analyst Philip Scholte.