Shuanghui International is close to securing shareholder approval for its US$4.7 billion offer for Smithfield Foods - which would be the biggest purchase of a US company by a Chinese firm - three people familiar with the matter said. The shareholder vote on Tuesday will be a key milestone that also raises pressure on activist investor Starboard Value, which opposes the transaction, to come up with an alternative plan for the world's largest pork producer. The deal needs the approval of just over 50 per cent of Smithfield shareholders. Shuanghui is well on its way to crossing that threshold with votes that have already come in and remains optimistic it will be able to close the deal by Tuesday, the sources said, asking not to be named because the matter is confidential. Hedge fund Starboard, which has a 5.7 per cent stake in Smithfield, has criticised the deal and has been working on lining up an alternative proposal. The fund is expected to make an announcement this week, although it is unclear if it will include a counterproposal, two other people familiar with the matter said. Industry bankers have expressed some scepticism about Starboard's ability to line up a new bidder for the firm, and the results so far show it may be running out of time. Shareholder votes, however, can still be changed. Smithfield and Shuanghui declined to comment, while Starboard did not immediately respond to requests for comment. An approval by Smithfield's shareholders would mark the end of a process that got mired in controversy earlier this summer as some US politicians expressed worries about food safety and domestic pork supplies if the company were to end up in Chinese hands.