U.S. Attorney General Eric Holder urged countries in Europe and elsewhere to do more to help decrease the flow of radicals traveling to Syria to fight with extremists during a speech in Norway on Tuesday. (Reuters)

Attorney General Eric H. Holder Jr. called on other countries Tuesday to develop a broad counterterrorism strategy to earlier identify radicalized individuals who are traveling to Syria and returning home as trained terrorists.

In a speech in Oslo before Norwegian diplomats, academics and national security officials, Holder recommended several steps for the United States and its allies to take to tackle the growing threat of foreign fighters in Syria.

Travel to Syria by Americans and Europeans to fight in the civil war there has become a major concern for U.S. and European law enforcement and intelligence officials. U.S. authorities confirmed last month that a 22-year-old American from Florida, Moner Mohammad Abusalha, carried out a suicide bombing in Syria in late May.

“This is a global crisis in need of a global solution,” Holder said. “The Syrian conflict has turned that region into a cradle of violent extremism. But the world cannot simply sit back and let it become a training ground from which our nationals can return and launch attacks. And we will not.”

Holder urged other countries to pass legislation that criminalizes “preparatory acts,” laws such as the material-support statute in the United States that allows law enforcement to arrest and prosecute individuals in the initial planning stages of terrorist plots. France and Norway enacted similar statutes in the past two years, and Norway, whose intelligence agency estimates that 40 to 50 of its citizens have traveled to Syria, charged the first person under its law in February.

U.S. officials have expressed concern in recent months that thousands of fighters are traveling to Syria from European countries and that many of them could then easily get into the United States under visa-waiver provisions.

“U.S. intelligence officials estimate that nearly 23,000 violent extremists are currently operating in Syria,” Holder said. “Among these are over 7,000 foreign fighters — among whom are dozens of Americans, a number that is growing.”

The attorney general also urged other countries to make greater use of undercover techniques. He pointed to the FBI’s strategy of conducting sting operations that identify U.S. citizens with extremist leanings and disrupt plots in their earliest stages.

“If we wait for our nations’ citizens to travel to Syria or Iraq, to become radicalized, and to return home, it may be too late to adequately protect our national security,” Holder said.

In recent weeks, according to a U.S. official, the FBI has arrested a couple from Texas who were about to board a plane to Canada in hopes of going to Syria, as well as a 19-year-old woman from Colorado who intended to travel to the region and link up with the Islamic State, a radical Islamist group that has overrun parts of northern and western Iraq.

As he did in a speech last month in Greece, Holder encouraged other countries to share more information about travelers to and from Syria. He urged greater reporting of data to Interpol so the United States and European nations can see more clearly which of their allies’ citizens have been to Syria.

In his Athens speech, Holder said the Obama administration will urge Congress to provide European Union citizens with the same rights as Americans, including the ability to sue in U.S. court, if any of their personal data is inappropriately disclosed after having been shared under a pending agreement. In return, he urged European countries to share more information with the United States about suspected terrorist activity.

The topic of foreign fighters in Syria is expected to dominate discussions with officials during Holder’s five-day trip to Norway and Britain, according to Justice Department spokesman Brian Fallon.

“We have a mutual and compelling interest in developing shared strategies for confronting the influx of U.S.- and European-born violent extremists into Syria,” Holder said in his speech. “And because our citizens can freely travel, visa-free, from the U.S. to Norway and other European states — and vice versa — the problem of fighters in Syria returning to any of our countries is a problem for all of our countries.”