The deal, if approved, would be the largest ever acquisition of a U.S. company by a Chinese firm.

The bid - an effort to feed a growing Chinese appetite for U.S. pork - has stirred some concern among U.S. politicians and faced review by a committee of several government agencies overseen by the Treasury Department.

The Committee on Foreign Investment in the United States (CFIUS) is an executive branch panel that examines foreign investment for potential threats to national security. It said in late July it would take a further 45 days to review Shuanghui's plan to purchase Smithfield, which was set to conclude by Saturday.

Smithfield, the world's biggest pork producer, declined to comment ahead of the panel's decision.

Some lawmakers expressed concerns the deal could jeopardize U.S. food safety and raise pork prices for American consumers.

However, most analysts familiar with the CFIUS process said the review was largely procedural and expected the deal to go through since there were no clear national security issues involved. (http://link.reuters.com/syf82v)

The source likened the case to the 2012 takeover of AMC Theaters by China's Dalian Wanda Group for $2.6 billion, which was allowed to proceed.

"We have theaters in military bases. We have ham in military bases," said the person, who was not authorized to speak publicly.

The Pentagon declined comment on the Smithfield case, referring all questions to the Treasury Department, which oversees the work of the CFIUS committee. Treasury also declined comment, saying by law, information filed with CFIUS may not be disclosed to the public.

While the Smithfield purchase is likely to clear one hurdle, it could face another in the bid by activist hedge fund Starboard Value LP to find a higher sale price for the pork company.

Starboard, a New York-based fund that holds a 5.7 percent stake in Smithfield, said in a letter to the company's shareholders on Tuesday that it had received indication that other parties may be willing to pay more than the $34 per share cash deal proposed by Shuanghui.

While the counter-proposal was not completed, the hedge fund said it planned to vote against the Smithfield-Shuanghui merger later this month in order to buy more time to get such a bid finalized.

(Additional Reporting by Sakthi Prasad in Bangalore; Editing by Matt Driskill)

By Anna Yukhananov and Andrea Shalal-Esa