It is not a matter of if, but of when the city’s subway system suffers a terrorist attack, Governor Spitzer’s pick as the state’s homeland security tsar, Michael Balboni, said.

Meanwhile, the Republican state senator who is resigning to join the new Spitzer administration said “not a lot is different” in terms of subway security since the attacks of September 11, 2001.

While he praised the ramped-up security at some tunnel entryways into the city as well as a greater police presence underground, he said the Metropolitan Transportation Authority has left gaping holes in the emergency preparedness of its conductors and train operators, who are responsible for initiating evacuations during emergencies. The MTA did not respond to a request for comment.

“There are some unspeakable potential threats out there,” Mr. Balboni said during a telephone interview over the weekend. “You can never guarantee that nothing will happen. All you can do is try to come up with new ideas and use cutting-edge technology.”

Mr. Balboni said his priorities include upgrading public transportation surveillance systems and beefing up security in suburbs surrounding the city that could act as staging grounds for terrorist plots.

He said Mr. Spitzer plans to improve the state’s relationship with Governor Corzine of New Jersey and to immediately address the vulnerabilities of the PATH tunnels. A recent internal Port Authority of New York and New Jersey memo said the tubes that the PATH trains run through are not strong enough to withstand even a small bomb attack.

Mr. Balboni’s positions on the city’s public transit system offer an early glimpse into Mr. Spitzer’s security priorities. Mr. Spitzer, who was sworn in as governor yesterday, has yet to outline a his own specific agenda for the transit system, but Mr. Balboni said the new governor has directed him to “run with the ball.”

One of his foremost goals will be securing more federal money to pay for essential security upgrades for the city’s aging subway infrastructure. Mr. Balboni said “major investments” must be made to the system’s critical infrastructure, including making subway entrances wide enough to allow for quick evacuations during emergencies.

Mr. Balboni — who served as chairman of the Senate’s Committee on Veterans, Homeland Security and Military Affairs — acknowledged the security improvements the New York City Police Department has already put in place, but said more needs to be done.

A police department spokesman, Deputy Commissioner Paul Browne, defended the security measures, citing the random bag searches and the increased number of police officers patrolling the subways. He said the measures have decreased the likelihood of a terrorist attack on the subway.

“It is disruptive of the kind of reconnaissance we know Al Qaeda engages in,” Mr. Browne said in an e-mailed statement. Mr. Browne also noted that conventional crime in the subways fell by 13% in 2006.

In addition, the police department has recently resuscitated its underground bomb-sniffing K-9 unit. Twenty-seven German Shepherds patrol the system as part of a new subway counterterrorism initiative.

Mr. Balboni warned, however, that any new surveillance must be weighed against privacy infringements. The MTA recently invested $5.2 million in a pilot project to equip 400 Manhattan buses with video surveillance systems, but Mr. Balboni called the program a “serious concern” from a civil liberties standpoint.

“Cameras don’t necessarily prevent anything from happening,” he said. “The effectiveness of the plan has to be measured against the loss of civil liberties.”

Mr. Balboni said he would also establish a “rapid information system” that will improve communication between local, state, and federal officials, as well as information sharing between the police department and the MTA.