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(CNN) -- The United States could have acted sooner to designate Boko Haram a foreign terrorist organization, a State Department official told Congress on Thursday, adding that "resolving this crisis is now one of the highest priorities of the U.S. government."
Robert Jackson, the principal deputy assistant secretary for African affairs, told a Senate subcommittee that the initial debate within the State Department over a terror label "was really about the Nigerian attitude towards designation" for the Islamic extremist group that advocates Sharia law.
"The government of Nigeria feared that designating these individuals and the organizations would bring them more attention, more publicity and be counter productive," said Jackson. "For some time we accepted that point of view."
Pressed by Sen. Marco Rubio, a Florida Republican, Jackson acknowledged that "in retrospect, we might have done it earlier. I think the important thing is that we have done it and that we've offered a reward for the top leadership of Boko Haram's location."
The group, which has claimed responsibility for kidnapping more than 200 school girls in northern Nigeria last month and threatening to sell them into slavery, was added to the terror list last November by Secretary of State John Kerry.
The timing of the action has triggered a political controversy around Hillary Clinton, who preceded Kerry as America's top diplomat and is weighing a potential run for president in 2016.
A formal terror designation provides greater access to a group's finances and more ability to limit its movements. Officials said Boko Haram does not have financing in the United States.
Some in Congress, the Justice Department and others called for the State Department to apply a terror label to Boko Haram in 2012 following a bombing in Abujat and amid growing concerns that it had al Qaeda links.
But the agency, then led by Clinton, rejected that approach. Officials cited the reasons raised by Jackson, which also included the possibility that doing so might heighten threats against U.S. and Western interests.
A letter to Clinton at the time by the 24 academics, including former U.S. Ambassador to Nigeria John Campbell of the Council on Foreign Relations, also said such a move would raise the group's profile and possibly link the United States to abuses by Nigerian forces cracking down on the group.
Republicans are now seeking to use the Boko Haram terror case as well as the deadly September 2012 terrorist attack on the U.S. diplomatic compound in Benghazi, Libya, to depict Clinton as complicit in what they argue is weakened foreign policy under President Barack Obama.
But former Assistant Secretary of State for African Affairs Johnnie Carson, who served under Clinton, told reporters last week that the convoluted socio-economic dynamics of Nigeria required a more holistic and nuanced approach than the security focus of anti-terrorism efforts.
"This is a very complex situation," he said.
Still, there was swift political reaction to Jackson's comments.
Correct the Record, a pro-Clinton rapid-response group, said "the facts are clear and hindsight doesn't change" things. It noted the State Department under Clinton placed three Boko Haram members on a terror blacklist.
The Republican National Committee also weighed in, saying Boko Haram was "another hard choice where Hillary made the wrong decision."
CNN's Tom Cohen contributed to this report.