President Barack Obama has nominated retired Gen James Clapper, a top Pentagon official, as his next intelligence chief.
If confirmed, he will replace Adm Dennis Blair, who resigned in May after a run of security failures, as director of national intelligence (DNI).
The new DNI will oversee 16 agencies in the intelligence community.
Mr Obama has urged the US Senate to confirm Gen Clapper's nomination swiftly.
Mixed reviews
Gen Clapper is likely to have a tough time winning over Capitol Hill.
Some in Congress have expressed objections to his nomination because of his combative style during hearings and his focus on defence department issues.
The senior Democrat and the senior Republican on the Senate Intelligence Committee, which will confirm Gen Clapper in his new role, had each previously publicly opposed his nomination.
"I don't think Clapper's the right person for the job," top Republican Senator Kit Bond told the Associated Press news agency.
Mr Bond argued Gen Clapper would not be able to command the authority needed for the position amid other strong personalities in the intelligence community.
Senior congressional staff told the Associated Press news agency that Mr Bond had not been consulted over who should fill the role, and that he might round up Republican support to block Gen Clapper's nomination.
Senator Joe Lieberman, chairman of the Senate Homeland Security Committee, told AP he thought Gen Clapper was a good match for the position.
Mr Lieberman said he looked forward "to working with him to determine whether the DNI needs additional authorities in order to lead and integrate the intelligence community".
The White House has had a difficult time replacing Mr Blair, who was forced out in a shake-up by Mr Obama.
The DNI came in for heavy criticism before Mr Blair's departure when the president's Intelligence Advisory Board delivered a report which asserted that the department was overstaffed and dysfunctional.
Close ties
Gen Clapper, who retired as a three-star general from the Air Force in 2005, served as the head of the National Geospatial-Intelligence Agency from September 2001 to June 2006, where he collected and analysed imagery.
In his current role, Gen Clapper has focused a great deal of his attention during the Obama administration on Afghanistan and Pakistan.
He is also a Vietnam War veteran and the former director of the Defense Intelligence Agency.
He has developed close ties to the intelligence community during his long career and is particularly close to senior managers at the Central Intelligence Agency (CIA), US media reports say.
If Gen Clapper's nomination is confirmed, he will be the fourth person to serve as DNI since the position was created five years ago on the recommendation of the 9/11 Commission.
