Shareholders of US oil and gas engineering companies McDermott International and Chicago Bridge & Iron (CB&I) have approved the merger of the two firms.

More than 50 per cent of McDermott shareholders supported the merger and approved a 3-to-1 reverse stock split. CB&I shareholders also voted in favour of the deal, the companies said, and the combination is expected to close on 10 May.

The merger, which was first announced by McDermott on 18 December, will create a vertically integrated onshore and offshore engineering and construction company that will work on a healthy order book of projects, as well as be well-positioned to win new projects both in the upstream and downstream sectors, particularly in the Middle East.

By way of winning shareholders’ approval, the last major step before the formal integration of the two companies, McDermott has also thwarted an attempt by Norwegian offshore drilling contractor Subsea 7 to block the deal by offering to acquire McDermott.

Oslo, Norway-based Subsea 7 said on Wednesday it had withdrawn its offer to buy McDermott and would seek other means of expanding its business.

In late April, it bid $2bn for McDermott and sought to halt its takeover of CB&I. McDermott last month had rejected Subsea 7’s offer, calling it “inadequate” and reiterating support for the combination with CB&I, which has been valued at roughly $1.68 billion.

As previously announced, upon completion of the merger transaction, McDermott stockholders will own approximately 53 per cent of the combined company on a fully diluted basis and CB&I shareholders will own approximately 47 per cent of the combined company.