AMSTERDAM (REUTERS) - Randstad, the world's second-largest staffing company, said on Tuesday it planned to acquire Monster Worldwide, the dotcom-era survivor that owns Monsterboard and Jobs.com, for US$429 million (S$577.7 million) on cash and assumed debt.

For Randstad, which has struggled to grow in the United States, the deal would fit into a series of acquisitions to expand into online recruiting.

Randstad is bidding US$3.40 in cash per Monster share, a 23 per cent premium to Monster's closing price Monday. The stock was up 3.5 per cent at US$26.17 at mid-afternoon on Tuesday. The bid follows Randstad's US$100 million purchase of United States startup RiseSmart in September.

Though Randstad has grown to rival global No. 1 Adecco in market capitalisation, it trails US market leader Manpower in North America.

Although Adecco and Manpower are Randstad's traditional rivals, the Monster acquisition appears calculated to counter a different sort of competitor: LinkedIn, which was recently acquired by Microsoft.

Ranstad Chief Executive Jacques van den Broek said that in addition to its strong US name recognition, Monster would bring a new technology platform and mobile phone presence to the Dutch-based company. Monster is known primarily for its mid-level jobs listings and its database of job-seekers' resumes.

Shares in Randstad slipped 3 per cent after the announcement of the deal. They ended 0.76 per cent higher at 39.76 euros.

In July, Ranstad reported second-quarter earnings before interest, taxation and amortisation (EBITA) of 240 million euros (S$355 million), up from 215 million euros in the year-ago period. However, its shares have suffered recently on concerns that Britain's vote to leave the European Union will hurt profits.

Randstad was advised on the deal by Wells Fargo and Jones Day acted as legal adviser. Monster's financial adviser was Evercore and its legal adviser was Dechert.