U .S.-led forces have killed two
The suspects, identified as Charaffe Mouadan and Abdul Qader Hakim, were among 10 Islamic State figures reported killed in targeted airstrikes over the last month.
Mouadan had been in direct contact with the suspected ringleader of the
He was "actively planning additional attacks against the West" and was killed in an airstrike over Syria on Dec. 24, Warren told reporters. He declined to provide further details.
French news reports, citing unidentified law enforcement officials, identified Mouadan as a French national of Moroccan descent who grew up in the Paris suburbs and was 26 or 27 years old.
He had been arrested in October 2012 with two friends, including Samy Amimour, one of the gunmen who took part in the Nov. 13 attacks in Paris. At the time, the trio was believed to be plotting to travel to Yemen or Afghanistan to take part in violent jihad, according to the French newspaper Le Parisien.
A French counter-terrorism official told Agence France-Presse news agency that Mouadan was not known to have strong ties to Abaaoud, who was killed in a police raid on an apartment on the northern outskirts of Paris five days after the attacks.
Hakim, a veteran fighter and forgery specialist, was also part of an Islamic State external operations group that enables attacks against the West, according to the Pentagon.
He had links to the Paris attack network and was killed Dec. 26 in an airstrike on the northern Iraqi city of Mosul, Warren said.
Other Islamic State operatives killed in the last month include finance and explosives experts, an executioner and a British-trained Bangladeshi hacker with expertise in evading electronic surveillance, Warren said.
None of these strikes is expected to deliver a knock-out blow to Islamic State, according to another U.S. official, who spoke on the condition of anonymity to discuss internal assessments. But officials contend that the cumulative effect of killing individuals in the group's middle and upper management could be significant in the long term.
Warren said recent battlefield successes, including the expulsion Monday of Islamic State fighters from a key government complex in the Iraqi city in Ramadi, were in part attributable "to the fact that this organization is losing its leadership."
"There's much more fighting to do," he said. "But our ability to dismantle the facilitation networks, our ability to dismantle their ground command and control, our ability to take away some of their enforcers ... that eats away at their ability to instill fear in the population they control, it eats away at their ability to extort money from the population, which of course, reduces their funding."
He also said, however: "We have not severed the head of this snake yet, and it has still got ... fangs. We have to be clear about that."
Islamic State is proving harder to degrade than its precursor and rival,
Eliminating an external operations figure in the Al Qaeda network was a "big deal," according to the U.S. official, because only a few individuals have the authority to plan and launch attacks against Western targets.
Islamic State gives greater autonomy to its members, and more of them are using their connections in Europe and other countries to inspire and plan attacks, the official said. That reduces the impact of the loss of any single individual.
The official noted that it was no surprise that a forger was among those targeted in the last month.
When Islamic State captured towns in Syria, the official said, the militants gained control of passport and identity card-making supplies as well as bank machinery that has allowed them to forge travel documents and financial statements to help members travel under aliases.
Questions have been raised about the validity of a Syrian passport found with the body of one of the Paris attacks who blew himself up outside a soccer stadium. He is believed to have posed as a refugee in order to travel from Syria to Europe to take part in the Nov. 13 assault, which also included attacks on cafes, restaurants and a packed concert hall.
Officials in France and Belgium, where most if not all of the attackers were from, have warned that more plots were believed to be in the works.
On Tuesday, the federal prosecutor's office in Belgium announced that two people had been arrested on suspicion of planning attacks in Brussels during the holidays.
The arrests followed searches on Sunday and Monday in the Brussels and Liege regions, as well as Flemish Brabant, that uncovered military-style training uniforms and propaganda materials from Islamic State. No weapons or explosives were found, the prosecutor's office said.