By Jeremy Pelofsky

WASHINGTON (Reuters) - FBI Director Robert Mueller on Wednesday urged Congress to be cautious about imposing strict rules on how and whether law enforcement officials can interrogate terrorism suspects they detain.

Some Republican lawmakers have questioned whether critical information was lost because the intelligence community was not present for interviews of a Nigerian man who tried to blow up a U.S. airliner on Christmas Day with a bomb hidden in his underwear.

Mueller said interviews often must happen quickly and getting the investigators who are specialists in certain subjects can take hours because they are hundreds of miles away, as was the case in the Christmas Day bombing attempt.

"We were dealing with on that day the necessity to respond, and within very few moments, to get the information that we thought was essential," Mueller told a House Appropriations subcommittee reviewing the FBI's fiscal 2011 budget request.

Authorities at the time were concerned the Nigerian man might have been part of a broader plot involving additional people carrying bombs on other planes.

"The one thing I do think is lost in some of this dialogue is that one has to make decisions relatively quickly in order to maximize the opportunity to get that information and intelligence," he said.

Legislation has been offered in the Senate aimed at forcing the Obama administration to have "suspected unprivileged enemy belligerents" held in military custody, interrogated for possible intelligence and tried in a military court.

A special team, known as the High-Value Interrogation Team, would recommend within 48 hours of detaining an individual whether the person would be placed in military custody, according to the legislation.

CAUTION

Mueller cautioned against tying the hands of law enforcement with more rules on interrogation.

"What I think our people did, and cannot be lost in the future, is to keep the opportunities open as long as you can and take advantage of those opportunities when they are presented," Mueller said.

The Nigerian man, Umar Farouk Abdulmutallab, was interrogated for about an hour by Detroit FBI agents before he underwent medical procedures for his injuries from the failed bombing attempt. After the procedures, they tried to interview him again, but he was less cooperative and stopped talking.

He was read his legal rights, sparking anger among many Republicans who said he did not deserve full U.S. legal protections. Obama administration officials have said they followed the same practice employed for many years.

Subsequently, the 23-year-old Abdulmutallab has begun cooperating again with investigators, in part because of intervention by his family and the prospect of facing the rest of his life in a U.S. prison, Mueller said.

Republican Representative Frank Wolf was involved in a heated exchange with Attorney General Eric Holder on Tuesday arguing that intelligence was lost in part because Abdulmutallab was not shown photos of potential terrorism suspects.

"I say it is true and you say it isn't true, but people that I've talked to said you missed an opportunity. You never had the pictures with you," Wolf said.

But Holder challenged the assertion that intelligence was lost.

"I have had access to the documents. I have access to the intelligence .... It is not true," Holder told lawmakers.

(Reporting by Jeremy Pelofsky, editing by David Alexander and Cynthia Osterman)