The US Coast Guard warned there were gaps in intelligence over the security risk of an Arab firm bidding to run six major US ports, the Senate has heard.
Dubai Ports hopes to take control of six major US ports
Senators opposed to the deal seized on the Coast Guard document to accuse the Bush administration of rushing to approve the takeover by Dubai Ports.
The government says it has addressed the concerns and the Coast Guard said the document was taken out of context.
A new opinion poll has shown 70% of Americans surveyed oppose the deal.
Dubai Ports (DPW) of the United Arab Emirates aims to take over the running of New York, New Jersey, Baltimore, New Orleans, Miami and Philadelphia from British-based P&O in a $6.8bn (£3.9bn) deal.
The administration gave the deal the green light but many lawmakers believe it increases the risk of terrorism.
US PORTS OWNED BY P&O
New York, New Jersey, Baltimore, New Orleans, Miami, Philadelphia
President George W Bush has agreed to a new 45-day inquiry into the matter, following the outcry from legislators.
But he has threatened to veto any legislation they might bring to try to block the deal.
At a Congressional hearing on Monday, Senator Susan Collins released an unclassified section of the Coast Guard document on the takeover.
The excerpt read: "There are many intelligence gaps concerning the potential for DPW or P&O assets to support terrorist operations, that precludes an overall threat assessment."
Ms Collins said the document suggested a "rush to judgment" by the administration.
"I believe the 45-day investigation should have been triggered by the transaction in the first place," she said.
The Coast Guard later released a statement saying: "The excerpts made public earlier today, when taken out of context, do not reflect the full, classified analysis performed by the Coast Guard."
The department of homeland security said again on Monday that it had asked for and received security assurances from DPW.
DPW has agreed to the new 45-day review and is still determined to proceed with the acquisition.
"We consider our company to be a friend of the United States," Michael Moore, a company executive told BBC Five Live.
In a new opinion poll for CBS News, only 21% of more than 1,000 respondents said they agreed the deal should go ahead, with 70% opposed.
Meanwhile, New Jersey officials are taking legal action to try and block the deal, and the Port Authority of New York and New Jersey is seeking to annul P&O's 30-year operating licence, claiming it failed to seek permission for the transfer of ownership.