The leftist government of Alexis Tsipras halted the port privatisation after winning elections in January last year but resumed the process under the 86 billion-euro bailout deal it agreed with its euro-zone partners in August.
Privatisations, a key element of Greece's bailouts since 2010, have produced revenue of only 3.5 billion euros so far. Athens concluded a 1.2 billion-euro airport leasing deal with Germany's Fraport in December, hoping this would help it to meet its target for privatisation proceeds of 3 billion euros this year.
The final bids for a 51 percent stake in Piraeus Port were submitted on Dec. 21. The prospective buyers were not made public although there was speculation that COSCO was the sole bidder. The privatisation agency said it will ask the bidder to raise its offer.
Greece has said that Cosco, Denmark's container terminal operator APM Terminals and Philippines-based International Container Terminal Services were interested in the sale.
The sale of a 51 percent stake in Piraeus could fetch about $179 million, based on the company's market value on Tuesday. Would-be buyers may opt to acquire an additional 16 percent stake over five years after completing mandatory investments of about 300 million euros.
The Piraeus port, a gateway to Asia, eastern Europe and north Africa, handled 16.8 million passengers and 3.6 million 20-foot equivalent units (TEUs) of containers in 2014.
Cosco has been operating one of the port's container terminals since 2009 and is investing 230 million euros to build a second container terminal at the port.
Cosco will merge with China Shipping in the Chinese government's latest effort to make the industry more competitive globally. A combined entity would be the world's fourth-largest container shipper, with a market share of roughly 8.1 percent.
Source: Reuters / Reporting by Angeliki Koutantou; editing by David Clarke