The man chosen by US President George W Bush to head the CIA has defended a controversial eavesdropping programme launched after the 9/11 attacks.
Gen Hayden must convince senators to back his nomination
General Michael Hayden ran the National Security Agency (NSA) in 2001 when Mr Bush approved the wiretapping.
He told a Senate committee the wiretaps were legal and used only to monitor those suspected of links to terrorism.
But he refused to comment publicly on reports the NSA also collected millions of domestic phone records.
He told members of the Senate Intelligence Committee he would speak in public only about programmes Mr Bush had confirmed.
A closed session was to be held later on Thursday.
Answering questions about the wiretap programme, Gen Hayden, a four-star air force general, said the rights of ordinary US citizens were of the utmost concern.
"Clearly the privacy of American citizens is a concern constantly," he said. "We always balance privacy and security."
Senator Ron Wyden, a Democrat from Oregon, asked Gen Hayden whether his record on the wiretap programme meant the senators should be concerned about his potential conduct if installed as CIA director.
"Well, senator, you're going to have to make a judgement on my character," Gen Hayden replied.
Opening the hearing, Democrat Senator Carl Levin described the CIA as being "in disarray", and asked whether Gen Hayden's appointment would restore independence and objectivity in the agency.
In response, Gen Hayden conceded that the CIA had become the "football of American political discourse," and said the agency needed "to get out of the news".
As director, he vowed to boost the use of "non-traditional" methods, and uphold the "risk-taking" heritage of the agency.
He pledged to develop the CIA's skills in human intelligence collection, and improve analysis methods.
"I would emphasise getting it right more often," he said.
"Intelligence works at the nexus of policy-making between the world as it is and the world we are working to create."
"When it comes to speaking truth to power, I will lead CIA analysts by example. I will - as I expect every analyst will - always give our nation's leaders the best analytic judgement."
In his opening remarks, Republican committee chair Pat Roberts said the surveillance programme was "tightly run and closely scrutinised".
"I am a strong supporter of civil liberties, but you have no civil liberties if you are dead," he added.
Gen Hayden was also expected to face queries from those concerned about a military officer heading the civilian CIA.
WHAT IS THE NSA?
US government intelligence service founded as a code-breaking agency in 1952
Intercepts communications using satellites and bugs
Said to be largest employer of mathematicians in the US
Budget and staff size classified
An agency as a whole so secretive its initials are said to stand for "No Such Agency"
The BBC's Adam Brookes, in Washington, says that despite expectations, Gen Hayden was not being given a particularly tough time by the committee.
On Wednesday, administration officials briefed members of Congress on the domestic wiretapping programme, a move analysts suggested could be aimed at easing the way for Gen Hayden.
As the hearings wore on, it seemed that many of the senators were reluctant to turn Gen Hayden's nomination into a big political battle, our correspondent adds.