U.S. authorities are monitoring a growing number of contacts between American extremists and foreign terrorist groups to make sure the two don't begin collaborating on attacks, government officials say. 

The officials caution there is no evidence to date that American extremists have been collaborating on any specific operations with European, Mideast or Asian terrorists. 

But they said they have evidence that neo-Nazis, white supremacists and Black Muslim factions have reached out to foreign terrorists whose similar hatred for Israel and the U.S. government might make them natural allies. 

"On the international terrorism front, we see people here and overseas communicating mainly via the Internet and talking back and forth and communicating that way," Dale Watson, the FBI's assistant director for counterterrorism, said recently. 

U.S. concerns about collaboration follows evidence from Europe detailing how Al Qaeda, the terror group headed by Usama bin Laden, and terrorists in the Middle East have been able to recruit like-minded citizens from France, Germany, Spain and Italy, officials said. 

Homeland Security Director Tom Ridge is aware there are contacts between American extremists and foreigners and backs the FBI's stepped up efforts, a spokesman said Wednesday. 

"It certainly is an area he is concerned about, and he is continuing to monitor these contacts," spokesman Gordon Johndroe said. 

The FBI is "going to investigate and follow any information that we have on any individuals or groups that may wish to cause harm to the United States, regardless of whether they are domestic or international," he said. 

For years, U.S. authorities have monitored efforts by neo-Nazis to stay in touch with like-minded groups in Germany and Western Europe. The FBI says the contacts are expanding beyond that universe. 

"We do see some interaction and communications between groups," Watson told the Senate Intelligence Committee earlier this month. "With the explosion of the Internet we certainly see white supremacist groups in contact with people in Europe, particularly in Germany." 

"We see more and more of that. That is a real growth area, and we'll see more of that," he told senators. 

The FBI official also raised concerns that Americans and foreigners might be beginning to use code words to disguise communications. "There are a lot of indicators and key things we look at, as well as the intelligence community, about codes, et cetera," Watson said. 

Officials and outside experts also are watching overtures by U.S. extremists to befriend Arab and Asian groups such as Hezbollah in Lebanon, Al Qaeda in the Mideast and Europe or abu Sayyaf in the Philippines. 

For instance, several anti-Israel Americans planned to meet in Lebanon last year for a major gathering of people who believe the World War II Holocaust did not occur. The Lebanese government forced the organizers, including a California group, to abandon the plans. 

A smaller but similar gathering was held later last year in Amman, Jordan. 

Such meetings allow Americans to befriend Arab extremists by focusing on a common hatred of Jews, one expert said. 

"That kind of event is where you make those contacts where the serious players are coming together. And it was on the Arab's home turf," said Mark Potok, a spokesman for the Southern Poverty Law Center that tracks American extremist groups. 

In the aftermath of Sept. 11, some American white supremacists have written pieces aimed at Middle Eastern or Muslim audiences that blame the attacks on the World Trade Center and Pentagon on U.S. politicians and Israel. 

"The real reason we have suffered the terrorism of the WTC attack is shockingly simple," former Klu Klux Klan leader David Duke wrote in one such piece. "Too many American politicians have treasonously betrayed the American people by blindly supporting the leading terrorist nation on earth: Israel." 

Duke's articles on his Web site are now translated into Arabic and have appeared in Mideast and Muslim publications since Sept. 11. 

A leading anti-Jewish advocate in Switzerland who has traveled to the United States was placed by on a U.S. list of foreigners whose assets should be frozen for aiding bin Laden's terrorist network. 

Albert Huber, a former Swiss journalist who converted to Islam, has been quoted in news stories as acknowledging he met at Islamic meetings with members of bin Laden's network and visited the United States. But he denies ever aiding terrorism. 

U.S. authorities also are watching to ensure extremist black Muslims, some of whom surfaced in earlier terrorism cases, don't become more activist. 

One Muslim from New York, Clement Rodney Hampton-el, is serving a lengthy prison sentence for his involvement in a failed plot to blow up the United Nations and other New York landmarks in the 1990s. He previously fought with Muslim rebels in Afghanistan. 

One of the groups being watched in the United States is al-Fuqra, a splinter sect of black Muslims that authorities have linked to several crimes over the past decade from Colorado to New York. 

A week after the Sept. 11 attacks, authorities charged three alleged al-Fuqra members living in a secluded trailer park near Roanoke, Va., with weapons and ammunition violations. 

Al-Fuqra was founded in New York city 20 years ago by a Pakistani cleric. The group "seeks to purify Islam through violence," according to a 1998 State Department report.