The US has given security clearance to Cosco Shipping Holdings's $6.3bn takeover of OOCL.
The Chinese state company said that the Committee on Foreign Investment in the United States cleared the deal for the Hong Kong container line.
It is thought to be the final piece on the regulatory jigsaw.
Cosco had already said on 29 June that all pre-conditions to the offer had been met when it won clearance from a Chinese anti-trust body.
In a regulatory filing on Sunday, the company said it had been notified that the committee did not have any outstanding security issues following an agreement with the US government to divest the Long Beach container terminal to a third party.
The Chinese shipowner said ownership of the terminal will be transferred to a trust while a buyer is sought.
It had been reported that the facility, worth $1.5bn, would be placed into a US-run trust to help secure approval.
The Chinese giant will become the third largest liner operator in the world after completion.
The deal creates an industry giant with more than 400 ships of a collective 2.9m teu that sits behind only Maersk Line and Mediterranean Shipping Company in the global standings.
