WASHINGTON, Feb. 27 — Coast Guard intelligence officials in December raised the prospect of significant security risks associated with the takeover of some American port operations by a Dubai company, saying in a previously undisclosed document that broad "intelligence gaps" prevented them from even assessing the possibility of a terror threat.

The Times"s David E. Sanger analyzes the latest news on the port takeover. "The breadth of the intelligence gaps also infer potential unknown threats against a large number of potential vulnerabilities," said the document released today at a Senate briefing into the port deal. It showed that Coast Guard analysts were worried about the backgrounds of employees of the company, Dubai Ports World, as well as the potential for foreign influences over the American ports and their use for terror operations.

The excerpt from the Coast Guard analysis was in contrast to the Bush administration"s assertions that the federal agencies responsible for reviewing the potential takeover offered no major objections, negating the need for an additional 45-day security review. The company has now been agreed to the additional review in the wake of the Congressional furor over the port deal.

Senator Susan Collins, Republican of Maine and the chairwoman of the Homeland Security and Governmental Affairs Committee, said the document unearthed by the committee"s staff left her troubled and skeptical that such extensive issues could have been resolved in the month before the deal was tentatively approved in mid-January.

"How, given the red flag questions that the Coast Guard raised, very serious questions about operations, personnel and foreign influence, how could there not have been the 45-day investigation that"s clearly required by law?" asked Ms. Collins, who today joined in introducing legislation that would give Congress final say on the port deal.

Administration officials appearing before the panel said the internal Coast Guard concerns were alleviated by a set of assurances from the Dubai company and the current port operator that participation in antiterror programs would continue.

"We negotiated unprecedented assurances from these two companies with respect to their security practices, assurances that I think addressed the question of what are their operations," said Stewart Baker, an assistant secretary for policy at the Department of Homeland Security.

The tough questioning at the Senate session illustrated that while the company"s agreement to undertake the 45-day review might have quieted the political battle for the moment, deep Congressional reservations remain even though Senator Bill Frist of Tennessee, the majority leader and an early critic of the deal, is now leaning toward support of the port sale.

In statements and comments to reporters in the past few days, Mr. Frist has said that private briefings by the Bush administration on its rationale for backing the port sale — combined with the agreement for a 45-day review — have answered many of his concerns, making it unlikely that he would support a quick push for legislation to block it.

"He is more comfortable with it than before," said Bob Stevenson, Mr. Frist"s spokesman.

The senator"s new position, criticized by some Democrats today as a flip-flop, left Mr. Frist more in line with such senior Senate Republicans as John Warner of Virginia, the chairman of the Armed Services Committee, who today stepped up his defense of Dubai and emphasized its strategic military value to the United States.

"It is the only port in the region that we can dock our major super carriers," Mr. Warner said on the Senate floor. "In addition, their airfields are supporting the ongoing operations that we have in Afghanistan and Iraq."