With New York City already under a heightened security alert, city officials yesterday announced a crackdown on drunken drivers during the summer season.

Mayor Michael Bloomberg said police, who this week began making random checks of vehicles using the Brooklyn Bridge and other potential targets of terrorists, will operate additional sobriety checkpoints in all five boroughs beginning Memorial Day weekend.

"Drunk driving is selfish, dangerous, and it kills," Bloomberg said in announcing an aggressive campaign against driving while intoxicated. Bloomberg, joined by Police Commissioner Raymond Kelly, said extra police will patrol the city's streets and highways during the campaign and reminded drivers that police will seize vehicles of motorists arrested on DWI charges.

"If you are thinking of driving drunk, don't, because we will take your car and send you to jail," Bloomberg said. "If you have been drinking, give your car keys to someone else or take a cab. Don't risk ruining your life to ending others' by getting behind the wheel."

"If you don't have a designated driver, Ray Kelly will provide one for you and I don't think you're going to like it," the mayor added. Kelly said drunken drivers will face jail time. "If you drive and drink, we will catch you, we will arrest you," he said.

Authorities said 36 sobriety checkpoints will be set up across the city during the weekend. In addition, the Police Department's Harbor Unit will enforce boating-while-intoxicated laws and will set up checkpoints along New York Harbor - the site of the 15th annual Fleet Week.

"With the heavy traffic that occurs during Memorial weekend, drinking and driving is even more dangerous than usual," Kelly said. "We want to make sure all the families that travel this weekend are safe."

There were 1,971 DWI accidents in the city last year - with 34 fatalities, authorities said.

Since the city instituted a policy of seizing cars in DWI cases in February 1999, police have confiscated 5,460 cars, including 647 this year, authorities said. Of those, 14 percent have been returned to owners under agreements mandating treatment and counseling for offenders.