A state trooper patrolling the underground concourse at the Capitol in Albany was knifed in the neck yesterday, police said.

Trooper Rodney Smith, 45, had stopped the man, described as in his 20s and homeless, to ask for ID at around 3:15 p.m. The perp whipped out a steak knife and stabbed Smith, just missing an artery.

The trooper is expected to recover. His attacker was still at large last night.