The takeover of US pork giant Smithfield Foods by China's Shuanghui International Holdings has received approval from a key US national security review, the two companies announced Friday.

The high-level Committee on Foreign Investment in the United States has approved the $7.1 billion deal, which would put the Chinese company in control of the world's largest swine grower and pork processor, they said.

The committee, which operates under the US Treasury, investigates any major foreign purchase of a US business that could be seen as damaging national security.

The clearance was an important hurdle to pass before the takeover goes ahead.

"We are pleased that this transaction has been cleared by CFIUS, and we thank the committee for its careful attention to this review," Smithfield chief executive and president Larry Pope said in a statement.

But the deal still faces a shareholder challenge. Earlier this week a key investor, Starboard Value, called on other shareholders to oppose the deal, arguing that the company would be worth more if broken up and sold piece by piece.