Turns out you can't do more with less.

Mayor Bloomberg admitted Friday the surprise uptick in murders could be linked to budget cuts that left fewer cops on city streets.

"It is worrisome," Bloomberg said of the 20% rise in murders this year, first reported in Friday's Daily News.

"We have fewer police officers than we did before," Bloomberg said. "More cops always helps."

The city's police force stands at approximately 35,000, down from its peak head count of 40,864 in 2000.

Bloomberg's latest budget plan would whack the department to its lowest level in two decades, leaving city streets with 32,817 officers come July.

"It's not going to particularly help the situation to go down another 2,000 officers," Police Commissioner Raymond Kelly said. "Are we concerned about it? Absolutely."

Making matters worse, an additional 3,150 officers may be laid off if Gov. Paterson's proposed budget - which contains $1 billion in cuts - is adopted. That would take the force down to under 30,000.

Bloomberg had previously boasted the NYPD can continue to drive crime down with fewer resources.

"All of the experts said it couldn't be done, particularly in a down economy, but we've done it," he gushed in December when he announced record-low murder numbers.

Lawmakers have been warning that whittling down the police force would lead to more crime.

"I believe even the mayor and Ray Kelly understand we've stretched the blue line to its limit," said City Councilman Peter Vallone (D-Queens). "Even the best force in the world can't continue to make gains against crime without any officers."

The growing murder rate could lead the city to pump more cash into hiring cops, Bloomberg said on WOR radio Friday.

There have been 103 murders citywide through Friday, up from 86 in the same period a year ago, NYPD statistics show.

Shootings are also up across the five boroughs, with 293 people struck by bullets through Sunday, a 16.3% change from the total of 252 a year ago.

The violent spike comes after a year in which the NYPD saw the fewest number of homicides on record. Kelly noted the city is still on pace for one of the lowest murder totals in history.

The city's top cop also admitted the jump in violence from 2009 had caught the NYPD's attention.

"This is our job No. 1," Kelly said. "We hope to change some tactics and strategies to make arrests, to continue to drive crime down and to stop the upward trend."