Bloomberg News A Cosco cargo ship sits docked at the Port of Vancouver terminal in Vancouver, British Columbia.Cosco Shipping Holdings Co., China’s biggest shipping company, agreed to buy smaller rival Orient Overseas (International) Ltd. Co. for $6.3 billion, establishing an Asian container giant at a time when the industry struggles to emerge from a multiyear down-cycle. The move will see a half dozen supercarriers grouped into three alliances, move about three quarters of all seaborne trade after a wave of consolidation among the world’s top 20 carriers over the past year. The Chinese conglomerate joined Shanghai International Port (Group) Co., one of the world’s biggest port operators, to buy a combined 68.7% stake from Orient Overseas’ controlling shareholder, Cosco 600026, +0.62% and Orient Overseas0316, +20.00% said Sunday in a joint statement. The offer price of 78.67 Hong Kong dollars per share (about $10.07) represents a 31% premium over Orient Overseas’ Friday closing price. The deal will have to be approved by global regulators, which is expected in the next six the eight months. An expanded version of this report appears on WSJ.com.