Although the Senate on Thursday approved one of President Bush's key Defense Department nominees, one senator is poised to block John Negroponte for the second-in-command slot at the State Department.

The Senate on Thursday confirmed Gen. George Casey to be the next Army chief of staff by an 83-14 vote.

But Sen. Russell Feingold, D-Wis., said he will place a hold on Negroponte's confirmation vote until Negroponte responds with answers to his questions. Any senator can place a hold on a nomination, effectively stalling the confirmation process. No other senators appear to have objections to Negroponte.

Negroponte is the outgoing director of national intelligence and is nominated to become deputy secretary of state. In a letter obtained by FOX News, Feingold said he is concerned that the recently distributed National Intelligence Estimate was politically motivated.

"While the NIE provides valuable intelligence assessments that will help inform policymakers, judgments about the deployment of coalition forces appear intended to advance the administration's political arguments. I ask therefore, that you, as the outgoing director of national intelligence, provide me information on any role that you or others in the administration may have played in framing the NIE," Feingold wrote to Negroponte.

"I further ask that you provide this information before the full Senate considers your nomination to be deputy secretary of state," the letter reads.

The Senate Foreign Relations Committee, of which Feingold is a member, on Thursday approved Negroponte's nomination on a voice vote. Negroponte must now face a full vote in the Senate, though he is expected to win approval handily.

Negroponte, who also has served as ambassador to Iraq and the United Nations, will fill the role of No. 2 at the State Department under Secretary of State Condoleezza Rice. Former Deputy Secretary of State Robert Zoellick left in July.

Casey will take over the spot being vacated by Gen. Peter Schoomaker, who is retiring. His confirmation was expected but did not come as easily as some other recent Bush administration changes. Some Republicans, including Arizona Sen. John McCain, said the four-star general should be held accountable for mistakes made in the Iraq war. Casey led troops in Iraq for more than two years.

On Wednesday, the Senate confirmed retired Navy Adm. Mike McConnell to replace Negroponte as President Bush's top intelligence adviser. McConnell, 63, a career military intelligence officer, will be responsible for coordinating all 16 intelligence agencies in the United States. The post was created to fill one of the recommendations of the Sept. 11 commission.

McConnell, a former director at the National Security Agency, has worked for the past decade for Booz Allen Hamilton Inc., a large defense and intelligence consulting company with sales of $3.7 billion worldwide. A specialist in the subjects of cyber security and critical infrastructure assurance, he has been earning a salary of almost $2 million a year.

McConnell's confirmation came alongside approval for Navy Adm. William Fallon, 62, to replace Army Gen. John Abizaid as head of U.S. Central Command. He will head to the region to join Gen. David Petraeus, who left for Iraq last week to replace Casey as head of Multinational Forces in Iraq. Abizaid is retiring.

FOX NEws' Trish Turner and The Associated Press contributed to this report.