WASHINGTON - Smithfield Foods Inc. said Wednesday that the U.S. government decided to conduct a second-phase review of its proposed merger deal with China's largest meat producer Shuanghui.

The Committee on Foreign Investment in the United States (CFIUS) , an inter-agency committee within the U.S. Department of Treasury, began to take an additional 45-day examination of the deal, which would be the biggest Chinese takeover of an American company, Smithfield said in a statement.

CFIUS is in charge of scrutinizing deals involving foreign companies for potential national security concerns. It can conduct a subsequent investigation after a standard 30-day review. After the two phases, CFIUS will submit a confidential report to U.S. President Barack Obama.

"Smithfield and Shuanghui International continue to expect the transaction to close in the second half of 2013," said the Virginia-based company.

Smithfield and Shuanghui International remain committed to working cooperatively with CFIUS throughout the process, it said, adding that they do not intend to comment further on the confidential CFIUS process.

In late May, Shuanghui agreed to acquire Smithfield, the world's largest pork producer and processor, for about 4.7 billion U.S. dollars. The Smithfield stock has risen 83 percent in the past 12 months and closed at 33.30 dollars per share Tuesday.