US President George W Bush has threatened to veto any move to block an Arab company's take-over of six of the biggest US seaports.
The state-controlled Dubai Ports World of the United Arab Emirates is on the brink of taking over the present ownership.
The ports, New York, New Jersey, Baltimore, New Orleans, Miami and Philadelphia, are currently owned and managed by the UK company, Peninsular and Oriental Steam Navigation Co.
P&O shareholders last week approved Dubai Ports World's $6.8bn takeover, which would create the world's third-largest ports group. A UK court is expected to give its final approval at a hearing next week.
Both Republicans and Democrats on Capitol Hill have questioned whether Dubai Ports World could be trusted to guard the ports if there was an increased threat of a terrorist attack.
Senior figures in both parties have drafted legislation to block the deal, while business interests and state governments have threatened legal opposition.
A similar hail of criticism from opponents last year drove off a bid by China's state-controlled CNOOC Ltd for the US oil company Unocal.
