WASHINGTON - Osama bin Laden's al-Qaida terrorist organization remains a threat to Americans around the world, despite a U.S.-led worldwide crackdown that has resulted in the apprehension of more than 1,300 extremists, the head of the CIA said yesterday.

"Al-Qaida leaders still at large are working to reconstitute the organization and to resume its terrorist operations," George Tenet told the Senate Armed Services Committee.

So far, the worldwide crackdown on al-Qaida has led to the arrest of 1,300 extremists with alleged links to the terrorist network in more than 70 countries and has stopped terrorist attacks in the works, said Tenet, director of the Central Intelligence Agency.

Some of those 1,300 extremists have been released from foreign custody, but it's unclear how many, U.S. officials acknowledged. In addition to those, more are in U.S. hands - in domestic jails, in Afghanistan, or at Guantanamo Naval Base in Cuba.

Nevertheless, many pockets of insurgents remain in the Afghan-Pakistan border area, and wiping them out could pose a bigger military challenge because they are in smaller groups of 10 men or so, Tenet said.

"As spring emerges, we'll see, maybe, more activity on their part," Tenet said.

Tenet, outlining a wide array of threats facing the United States from countries including Iraq, Iran and North Korea, also told Congress that the United States is losing its longtime superiority in satellite reconnaissance.

China and India are developing increasingly sophisticated satellites, and much of the most-sophisticated imagery is also available commercially, Tenet said.

"The advantage we have enjoyed is eroding," Tenet said.

Tenet said the United States believes Iraqi President Saddam Hussein never abandoned his program to try to develop nuclear weapons. But he refused to talk publicly about the possible strength of opposition groups inside Iraq, telling senators he would discuss such issues with them later in a closed session.

U.S. officials previously have said that al-Qaida has stepped up its financial activity markedly in recent weeks, suggesting some leaders are reasserting control and may be seeking to finance more attacks against American interests.

The increased flow of money corresponds with a recent increase in communications between surviving al-Qaida members, one official said last week, speaking only on condition of anonymity.

The communications, detected by U.S. intelligence, have occurred between small groups of al-Qaida fighters and some Taliban allies, officials said. Much of the activity is centered in northwestern Pakistan - near the Afghan border - although some money and communications are going elsewhere, one official said.

The activity suggests some known al-Qaida leaders are re-establishing control over surviving elements of the terrorist network, the official said, declining to name the leaders.

U.S. intelligence also has detected a significant boost in money transfers within al-Qaida to people who could use it to prepare attacks on American interests, although the official offered no specifics on potential attacks.

The fate of many of al-Qaida's top commanders is unknown. While several have been killed in the Afghan war, and a few captured, many are believed to have hidden in caves in Afghanistan to wait out the U.S. bombing campaign. Bin Laden himself has been silent for months.