FBI Director Robert Mueller says transatlantic cooperation against terrorism is improving - and is vital for Europe and the United States to be able to successfully counter threats. Mueller is on a tour of Europe that includes a stop in Paris. Lisa Bryant has more from the French capital.

Speaking to reporters Friday, FBI Director Mueller pointed to the case of Germany - where officials recently dismantled an alleged bombing plot - as just one example of why transatlantic cooperation is critical.

"We work closely with our German counterparts to address the threats within Germany," he said. "But the arrests in Germany are yet another indication for us all to be vigilant, because terrorism, like so many crimes, crosses borders easily, it's the exchange of information and the development of relationships that will enable us to be successful against those who present a threat within our borders."

Also vital, Mueller said, was sharing intelligence - so long as national judicial traditions and laws are respected.

"In this world today it's absolutely essential that you have the free exchange of information. So we have to do it within our different judicial frameworks," he said.

Mueller spoke following a morning meeting with French Justice Minister Rachida Dati. He later met with France's interior minister and other top officials. He described counter-terrorism cooperation with France as historically good and improving under the country's new president, Nicolas Sarkozy. He pointed to exchange programs involving French and American judges as one example of cooperation.

Like the United States, the fight against terrorism is a top political issue in Europe, which has witnessed two major terrorist attacks - in Madrid and London - since the September 2001 strikes in Washington and New York.

Mueller arrived here from Austria, where he met with Austrian officials to discuss recent arrests in Vienna of two suspected members of the al Qaida terrorist group - and to assess the chances of terrorism during a Euro soccer tournament scheduled there next year. He heads next to the Baltics.