The U.S. government is expected to formally apply a "foreign terrorist" label Today to three alleged leading figures of the violent Nigerian militant group Boko Haram, officials said.
The action by the State and Treasury departments follows growing pressure on the Obama Administration to take stronger action against Boko Haram.
The group, which says it wants to establish an Islamic caliphate in northern Nigeria, has stepped up attacks on Christian places of worship this year.
Thursday's anticipated action, officials said, involves applying the "terrorist" designation to three men presumed to be central figures in the group.
The three individuals, an official said, are Abubakar Shekau, aged around 43, described as a Boko Haram leader who allegedly aligned himself with al Qaeda in a video message; Abubakar Adam Kambar, aged roughly 35; and Khalid al Barnawi, aged approximately 36. All three are native Nigerians.
The expected action will freeze any assets they have in the United States and bar U.S. persons from any transactions with them.
It is among the first such action the U.S. government has taken against Boko Haram, but falls short of demands from some U.S. lawmakers and the Justice Department to designate the entire group as a "foreign terrorist organization."
The State Department has been under pressure to act against Boko Haram for months. In January, Lisa Monaco, the Justice Department's top national security official, sent a letter to the State Department arguing that the Nigerian group met the criteria for a "foreign terrorist" listing because it either engages in terrorism that threatens the United States or has a capability or intent to do so.
Boko Haram increasingly is seen as a potent threat to Nigeria, the continent's most populous state and major oil producer, and as part of growing arc of Islamist extremist groups stretching across northern Africa.
More recently, a group of Republican senators led by Scott Brown of Massachusetts introduced legislation requiring the State Department to determine whether Boko Haram should be designated as a terrorist group.
Republican Representative Patrick Meehan, who chairs a Homeland Security subcommittee in the House, also introduced an amendment that would force the administration to add Boko Haram to the terrorism list or explain why it was not doing so.
However, U.S. diplomats are weighing these demands against counter arguments, including those made by a group of academic experts on Africa who sent a letter to Secretary of State Hillary Clinton last month urging her not to designate Boko Haram as a terrorist group.
The academics argued that the move could backfire by enhancing the group's reputation among potential recruits and other militant groups. A U.S. designation might also empower more radical elements of Boko Haram, which is divided into factions, the professors said.
In her letter to the State Department, Monaco of the Justice Department reported that since 2009 Boko Haram has conducted violent attacks against Nigeria's "police, politicians, public institutions and civilian population."
Monaco said that according to press reports, Boko Haram claimed responsibility for 510 victims in 2011, and also took credit for a January 20 attack on government buildings in Kano in which more than 160 were killed.
She said that although Boko Haram attacks until now have occurred only within Nigeria, Washington should not underestimate the threat the group poses to U.S. interests.