It is not clear which American company is willing to buy DP World's U.S. operations. About 75 percent of containers that enter U.S. ports go through terminals that are operated by foreign-owned firms.

Officials at Seattle-based SSA Marine, the largest U.S.-owned terminal operator, said they have not been contacted. Some potential bidders may seek to join forces with firms that already have operations at U.S. ports. But the process is in the early stages, and DP World appears to be determined to avoid a fire sale.

One potential private-equity buyer is Washington's Carlyle Group, which bought the U.S. container-shipping business of CSX Corp. in 2002 for $300 million, selling it two years later for $650 million. Also, the Dubai government has been an investor in Carlyle's investment funds and put $100 million into its latest, $7.85 billion buyout fund.

A source at Carlyle, however, said the firm will probably not be interested in P&O's port operations, given the political scrutiny such a deal would invite.

Another potential private-equity buyer is the Blackstone Group of New York. Though not ruling out an offer for the business, a source at the firm said it is too early to tell whether P&O's U.S. operations are even worth seeking.