"We're not aware of a single national security concern raised recently that was not part of the multi-agency, three-month review," Deputy Treasury Secretary Robert Kimmitt told a Senate Armed Services Committee briefing.
Representatives of key agencies that investigated the port deal - but not the heads of the various departments - sought to reassure senators just hours after US President George W Bush declared "people don't need to worry about security."
Brushing aside President Bush's assurances, Senator Carl Levin, the panel's ranking Democrat, said the UAE was "one of only a handful of countries in the world to recognise the Taliban regime in Afghanistan." He said millions of dollars in al-Qaida funds went through UAE financial institutions.
Senator Hillary Clinton called the approval process "a failure of judgment" because officials "did not alert the president, the secretary of the treasury and the secretary of defence" that several of America's critical ports would be turned over to a foreign country.
Senator John Warner, Republican chairman of the committee, emphasised UAE's co-operation in the war on terrorism, noting that it allows a large number of port calls by US military and commercial ships and that it had made its airfields available to the US military.
Mr Bush, talking to reporters after a Cabinet meeting earlier in the day, said he was struck by the fact people were not concerned about port security when a British company was running the port operation, but felt differently about an Arab company at the helm. He said the UAE was a valuable partner in the fight against terror.
"It's really important we not send mixed messages to friends and allies around the world as we put together a coalition to fight this war on terror," he said.
The controversy is the latest blow to an administration reeling from setbacks in Iraq, criticism of its response to Hurricane Katrina and a series of criminal investigations affecting Republicans in Congress and the White House.
Under secret conditions of the agreement with the administration, the Dubai company promised to co-operate with US investigations as a condition of the $6.8 billion (€5.7bn) deal, according to documents obtained by the media.
The US Government chose not to impose other, routine restrictions.
Critics in Congress, even before yesterday's hearing, had noted that London-based P&O, which previously operated at those ports, is a publicly traded company while Dubai Ports World is effectively controlled by the government there. Senators Robert Menendez and Clinton have said they will introduce legislation to prohibit companies owned or controlled by foreign governments from running port operations in the US.
Mr Bush said his administration would continue talks with members of Congress who have rebelled against the takeover.
Even before the controversy erupted, the Dubai company had hired former Senate Majority Leader Bob Dole's law and lobbying firm, Alston and Bird LLC, to win approval for the deal. The Albright Group, led by former Secretary of State Madeline Albright, has also been trying to speak with members of Congress.