Lawmakers asked the White House to reconsider the deal. The sale to state-owned Dubai Ports World was "rigorously reviewed" by a US committee that considers security threats when foreign companies seek to buy or invest in American industry, Frederick Jones, a National Security Council spokesman, said on Thursday.
The Committee on Foreign Investment in the US, run by the Treasury Department, took into account an assessment from US intelligence agencies. The committee's 12 members agreed the sale did not present any problems, the department said.
The public defence of the secretive committee, which reviews hundreds of such deals each year, came in response to criticism about the purchase of London-based Peninsular and Oriental Steam Navigation Co.
The world's fourth-largest ports company runs commercial operations at shipping terminals in New York, New Jersey, Baltimore, New Orleans, Miami and Philadelphia.
Four senators and three House members asked the administration on Thursday to reconsider its approval. The lawmakers contended the UAE is not consistent in its support of US terrorism-fighting efforts.
"The potential threat to our country is not imagined, it is real," Mark Foley, a House member, said in a House speech.
DP World said it had received all regulatory approvals for its purchase and noted that the administration did not object.
The US describes the UAE as a
vital partner in the war on terror
"We intend to maintain and, where appropriate, enhance current security arrangements," the company said in a statement. "It is very much business as usual for the P&O terminals" in the US.
Lawmakers said the UAE was an important transfer point for shipments of smuggled nuclear components sent to Iran, North Korea and Libya by a Pakistani scientist, Abdul Qadeer Khan.
They also said the UAE was one of only three countries to recognise the now-toppled Taliban as Afghanistan's legitimate government.
The State Department describes the UAE as a vital partner in the fight against terrorism. Dubai's own ports have participated since last year in US efforts to detect illegal shipments of nuclear materials.
Vito Fossella, a House member, urged congressional hearings on the deal.
"At a time when America is leading the world in the war on terrorism and spending billions of dollars to secure our homeland, we cannot cede control of strategic assets to foreign nations with spotty records on terrorism," Fossella said.
Critics also have cited the UAE's history as an operational and financial base for the hijackers who carried out the attacks of 11 September 2001.
"Outsourcing the operations of our largest ports to a country with a dubious record on terrorism is a homeland security and commerce accident waiting to happen," said Charles Schumer, a senator.
"The administration needs to take another look at this deal."