President Reagan's recent executive order expanding the powers of the Central Intelligence Agency within the United States ''opens up the opportunity to intrude into the private lives of Americans,'' says former CIA Director Stansfield Turner.
While generally supportive of the President's moves to strengthen the CIA, the retired admiral said broadening intelligence-gathering powers at home is ''risky'' in that it could revive public distrust of the agency and ultimately weaken its capabilities.
In issuing his order, the President said ''no intelligence agency . . . will be given the authority to violate the rights and liberties guaranteed . . . by our Constitution. . . .''
''It's not just that none of us wants to undermine the constitutional rights of privacy,'' Mr. Turner told a breakfast meeting of reporters. ''But the CIA is not trained to operate within the constraints of American law. That's the FBI's role.''
The former Carter administration official also is critical of the direct role that congressional intelligence committees apparently played in formulating the Reagan administration's new thrust for the CIA.
''This weakens the . . . oversight process,'' he said. ''We now have the Congress co-opted from its normal oversight role.''
Since reentering private life, the former CIA chief has continued to write and speak on intelligence and military affairs. He favors increased strength in both areas, but disagrees with the current administration in some aspects of meeting this goal.
Regarding the relative military might of the Soviet Union and the US, Turner says the administration is unduly emphasizing strategic power and fixed overseas bases at the expense of strengthening an ''expeditionary force'' to meet Soviet third-world thrusts.
Each country has certain strategic advantages over the other, he says, but the US still is strong enough in its nuclear capability to deter the USSR from initiating a nuclear war. However, he agrees that the Soviets ''are ahead and moving further ahead'' in Europe.
''There is no way you can negotiate Western Europe out of nuclear vulnerability,'' he warned. ''We should be very careful that we don't negotiate away too much in order to give the West Europeans confidence.''