WASHINGTON - The State Department will formally designate the Nigerian Islamist militant group Boko Haram as a "foreign terrorist organisation" on Wednesday, congressional sources and others briefed on the matter said.
The designation is significant because it directs US law enforcement and regulatory agencies to block business and financial transactions with Boko Haram, which wants to impose Islamic law in northern Nigeria and has ties to al Qaeda.
The move makes it a crime under US law to provide "material support" to the group. A State Department spokeswoman did not immediately respond to a request for comment.
Boko Haram and other splinter Islamist groups are seen as the biggest security threat in Nigeria, Africa's most populous country and top oil exporter.
In May, President Goodluck Jonathan increased a military campaign against Boko Haram. His government said last week that it has killed 70 civilians.
The House Foreign Affairs Committee, which a source said has been notified of the decision, has scheduled a hearing on the group for Wednesday.
"The likelihood of more hearings on this issue may have been a final straw in encouraging the State Department to acknowledge something which has been apparent for some time - the growing relationship between Boko Haram and al Qaeda in the Arabian Peninsula," said US Rep. Patrick Meehan, a Pennsylvania Republican who convened his own hearing on the issue.
Meehan chairs a Homeland Security subcommittee, not a Foreign Affairs committee, and has not been briefed by the State Department. "Boko Haram is of growing influence and of major concern," he said.
Last year, the Justice Department's senior top national security official, Lisa Monaco, sent a letter to the State Department arguing that Boko Haram met the criteria to be listed as a "foreign terrorist" group because, she said, it either engages in terrorism that threatens the United States or has a capability or intent to do so.
Monaco is now President Barack Obama's top White House counter-terrorism advisor.
Although the State Department later designated three alleged Boko Haram leaders as terrorists, it stopped short of a more sweeping declaration against the organisation.
For two years, Meehan and Rep. Peter King of New York have pressed the State Department to put Boko Haram on its list of terrorist groups alongside the likes of al Qaeda and Lebanon's Hezbollah.
They have warned that an August 2011 attack on a UN building in Abuja, Nigeria, marked a turning point as a threat to US interests. Meehan has noted that the United States did not perceive al Qaeda in the Arabian Peninsula as a threat to US interests until after the attempting downing of an airliner by a Nigerian near Detroit on Christmas Day, 2009.