The U.S. is planning a "major" new security program to help Nigeria battle Boko Haram terrorists, a senior State Department official said in the Nigerian capital of Abuja on Thursday.

"Despite our collective efforts, the situation on the ground is worsening," the assistant secretary of state for Africa, Linda Thomas-Greenfield, told a meeting of officials from the U.S. and Nigeria, the Associated Press reported.

The frequency and scope of Boko Haram's terror attacks have grown more acute and constitute a serious threat to this country's overall security.

This is a sober reality check for all of us. We are past time for denial and pride."

Thomas-Greenfield said Boko Haram may try to attack the critical city of Maiduguri and that the U.S. was preparing a major border security program along with Nigeria, Camaroon, Chad and Niger, according to Bloomberg News.

In 2009, a conflict between Boko Haram and the security forces in the populous city left at least 700 dead. Reuters has reported that hundreds have already fled in fear of the group's advance. 

The State Department designated Boko Haram a terrorist group in 2013, and it drew international condemnation earlier this when it kidnapped hundreds of Nigerian schoolgirls with the intention of selling them into slavery.

The group has been seizing land in northeast Nigeria and proclaiming an Islamist caliphate, the AP reported.