White House counterterrorism chief John O. Brennan said Friday that European failure to join the United States in designating the Lebanon-based militant group Hezbollah a terrorist organization is undermining international counterterrorism efforts.

“Let me be clear,” Brennan said in a speech in Dublin, European resistance “makes it harder to defend our countries and protect our citizens.”

Brennan listed Hezbollah at the top of a list of joint U.S. and European security challenges. In addition to its alliance with terrorist activities by Iran, he said, “we have seen Hezbollah training militants in Yemen and Syria.”

The Obama administration has previously accused Hezbollah of training Syrian government forces fighting an armed uprising in that country. Early this year, it also charged Hezbollah with facilitating Iranian arms shipments to Shiite separatists in Yemen, although it did not say there was on-the-ground training there.

The United States first designated Hezbollah as a “global terrorist” organization in 1995, seizing U.S. assets and prohibiting anyone in this country from providing it with material or financial support. While some countries in the European Union, including Britain and the Netherlands, have argued the Europeans should follow suit, the E.U. and individual governments have argued that there is no tangible evidence the group has undertaken terrorist acts in Europe.

Ransom payments, he said, “many of which come from Europe,” create a “vicious circle — fueling the very criminality, violence and terrorism that we seek to stop.”

“From President Obama on down, we continue to urge our allies and partners to resist the temptation to pay,” Brennan said.