The State Department says it is adding Abubakar Shekau, Abubakar Adam Kambar and Khalid al-Barnawi to its list of terrorists. That means they are not allowed to hold property or assets in the United States and that Americans are prohibited from dealing with them.
State Department spokeswoman Victoria Nuland says the three men will no longer be able to use the United States to raise funds for their group.
"It also sends a shot across the bow [a warning] to those who are considering taking up extreme violence to address grievances in the north [of Nigeria] that this is a course that is open to us with regard to them as well," said Nuland.
Boko Haram has claimed responsibility for many attacks in Nigeria, including the bombings of several church and the United Nations headquarters in Abuja, as well as a series of attacks in the city of Kano that killed more than 180 people.
The State Department says Kambar and al-Barnawi have close links to al-Qaida in the Islamic Maghreb. Shekau is Boko Haram's "most visible leader" in the push for an Islamic state in the north outside of Nigeria's federal constitution.
The terrorist designations stop short of naming Boko Haram a terrorist organization, something that is gaining support in the U.S. Congress and at the Justice Department.
The State Department's Victoria Nuland says the Obama administration is "continuing to look at that," but there is always the question of whether the terrorist designation of individuals within an organization is a more effective strategy.
"Boko Haram is, at the moment, a loosely constructed group attached to trying to address grievances in the north," she said. "There are different views within the group, and we are continuing to look at that."
Nuland says the United States is working with the Nigerian government to address some of the underlying causes of Boko Haram violence by promoting a unified, pluralistic nation where the rights of all people are protected, regardless of region or ethnicity.
"And that it begin a real dialogue about some of the roots of the dissatisfaction in the north, which are primarily economic, and that they have got to really engage the northern communities and thereby make them more resistant to some of these extremist-style tactics that these three [individuals] espouse," said Nuland.
Nuland says there has been discussion at the presidential level between the United States and Nigeria in recent few months about how best to address the Boko Haram problem.
"We are making some progress in terms of our security relationship with them, encouraging them to strengthen policing versus using the military in these cases," she said. "And we are working with them on the kinds of offers of dialogue, economic support, etc., that could be helpful."
Nuland says the United States is concerned about links between Boko Haram and al-Qaida in the Islamic Maghreb and that it is working with governments in the Sahel "to close space for terrorism" in the region.
STATE DEPARTMENT - The United States on Thursday designated as terrorists three members of the Nigerian militant group Boko Haram. The Obama administration says it is working with the government in Abuja to address some of the social and economic problems underlying the violence in northern Nigeria.