Thousands of New Jersey police officers and firefighters may have to change their retirement plans starting Jan. 1 because of changes to federal pension rules.

The changes are set to take effect in 2009 and could put an end to one benefit of a dangerous career: the "25 and out" rule.

The idea behind the rule is that if a police officer or firefighter gives 25 years of service, then they can retire, often in their early 40s.

The new rule would require people in these fields to work until age 50.

Police officials say they predict many officers who have worked their 25 years will make a dash for retirement before Jan. 1. For others who started working at age 20 and planned to retire next year at age 45, they'll be forced to stay five more years.

According to the Police Benevolent Association, 1,000 cops between the ages of 40 and 50 retired last year. The union now fears even more will rush to retire this year while they still can, creating staffing problems in police departments across the state.

The PBA says it's working with Congressman Bill Pascrell of the House and Means Committee to fight the change.