The US Senate has unanimously confirmed federal judge Michael Chertoff as the new secretary of homeland security.
Michael Chertoff testified against the use of torture in interrogations
His confirmation fills the last vacancy in President George W Bush's cabinet.
Mr Chertoff, 51, has promised to balance the challenge of protecting the US from future acts of terror with the need to preserve civil liberties.
The former assistant attorney general, who played a key role in the legal response to the 11 September attacks, replaces Tom Ridge in the post.
The Senate's 98-0 vote on Tuesday puts Mr Chertoff in charge of a sprawling two-year-old department, created with responsibility for preventing future terror attacks on the US.
He promised that if approved he would "devote all my energy to promoting our homeland security and, as important, to preserving our fundamental liberties".
During his confirmation hearing two weeks ago, he testified against torture and told the hearing that officials should ensure interrogations were conducted "well inside the law".
He was directly consulted by the CIA and US officials over interrogation policies for Abu Ghraib prison in Iraq, the Guantanamo Bay naval base in Cuba and in Afghanistan.
Mr Chertoff also faced pointed questioning from Democrats at the hearing over his role in developing the US investigation immediately after the 11 September attacks.
From 2001 to 2003 he headed the justice department's criminal division, which has been criticised over its treatment of some of the hundreds of foreigners who were detained in the days following the attacks.
Mr Chertoff defended the investigation strategy but acknowledged it "had not always been executed perfectly".
On announcing his nomination, Mr Bush praised Mr Chertoff as "a practical organiser, a skilled manager and a brilliant thinker".
"In the days after 11 September , Mike helped trace the terrorist attacks to the al-Qaeda network. He understood immediately that the strategy in the war on terror is to prevent attacks before they occur," Mr Bush said.
Mr Chertoff was, however, Mr Bush's second choice for the homeland security post, put forward after ex-police commissioner Bernard Kerik withdrew his name because of questions over the immigration status of his housekeeper.