FBI Director Robert Mueller on Wednesday called for changes in federal law to help his agents with surveillance of communications in anti-terrorism and other criminal investigations.

At a conference of intelligence experts, Mueller said that in some instances communications companies are unable to provide electronic communications the FBI seeks in response to court orders.

His comments came as the Obama administration considers proposals that would require service providers to make the plain text of encrypted conversations — over the phone, computer or e-mail — readily available to law enforcement.

The FBI's general counsel has said proposed changes would not expand law enforcement authority, but privacy advocates disagree.

Mueller said some people have suggested there is an inherent tension between protecting national security and preserving civil liberties.

"I disagree," he said. "We have a right to privacy, but we also have a right to ride the subways without the threat of bombings. ... It is a question of balance."

"If we safeguard our civil liberties, but leave our country vulnerable to a terrorist attack, we have lost. If we protect America from terrorism but sacrifice civil liberties, we have also lost," he said.

Gregory T. Nojeim, who is with an Internet privacy group, said that backdoors built into communications applications to facilitate FBI access will be exploited by hackers and ID thieves and will make the public less secure.

"We're in the middle of Cybersecurity Awareness Month and the FBI is proposing anti-cybersecurity," said Nojeim, director of the Project on Freedom, Security and Technology at the Center for Democracy and Technology.