U.S. Homeland Security Secretary Michael Chertoff says the United States sees an increasing threat of terrorist attacks coming from Western Europe. Tendai Maphosa has more in this report for VOA from London.

Speaking on British radio and television, BBC TV and radio,  Michael Chertoff pointed to the rise of what he called "home grown terrorism" in Europe and warned that Western Europe could increasingly become a breeding ground for terrorists.

In the interview, Chertoff said the United States is looking at measures to tighten security, including checks on travelers coming into the United States from Western Europe. He said such checks are necessary.

"We have a visa waiver program that allows most Europeans who come to be tourists to travel without a visa," Chertoff said. "That means the first time we encounter them is when they arrive in the United States and that creates a very small window of opportunity to check them out."

Chertoff did not specify what measures might be taken to try to weed out potential terrorists, but said steps would be taken to avoid travel and business from being negatively affected.

"A lot of what we are trying to do is find a way to better vet [screen] people coming from Europe without impeding the flow of travel and trade which has been a very important part of our economy," said Chertoff.

Chertoff cited the Madrid bombings in 2004 and subsequent bombings and foiled attacks in Britain as evidence that terrorists are increasingly looking to Europe both as a target and as a platform for attacks.

But International Affairs analyst Michael Cox of the London School of Economics tells VOA that while he understands U.S. concerns, he does not believe the U.S. government will go as far as requiring Western European travelers to apply for visas to visit the United States.

"They are not going to get rid of the visa waiver program," said Cox. "It's too problematic, too difficult to do so it would send the wrong political signal. And, secondly it would slow down things enormously. What they [the US] will require is that people register before they go."

"So I think there will be, at least I think 48 hours or 72 hours before you fly or even more, you will have to go through a registration through a central computer system that gives them more time to check up on people," he added.

Cox said he does not believe such a program would have a great impact on European-U.S. relations if it is implemented. He said it might be an inconvenience but people have become more accustomed to such restrictions.