OKLAHOMA CITY (AP) - Under attack for his spending habits in Congress, Republican presidential candidate Rick Santorum defended his use of earmarks, saying Thursday that some were necessary for defense or health programs.

With the ex-senator's surprising climb back into contender status with a trio of wins this week in the race to become the GOP's presidential nominee, Santorum has become the subject of biting criticism from rival Mitt Romney.

The former Massachusetts governor is challenging Santorum's
commitment to fiscal discipline by pointing out spending set-asides
he sought during the days when he represented Pennsylvania in
Congress.

The taint of earmarks, or spending that lawmakers direct to favorite projects, still dogs candidates courting the fiscally conservative tea party movement, which explains why Romney and his allies have been pounding Santorum on the issue.

Santorum upset Romney this week by winning nominating contests in Colorado, Minnesota and Missouri.

Campaigning in strongly conservative Oklahoma, Santorum defended
his record and argued that earmarks were a legislative check on the
executive branch.

"There are good earmarks and bad earmarks," he told reporters after a speech.

Santorum specifically defended targeted spending for the V-22 Osprey helicopter and a human tissue medical program in Pittsburgh.
He declined to identify any earmarks he regretted.

On Wednesday, Romney said Santorum and former Speaker Newt
Gingrich belong to a category of Republicans who "spent too much
money, borrowed too much money, earmarked too much."

Santorum said Thursday that he fought to end earmarks amid concerns that lawmakers were abusing the practice. He tried to turn
the issue back on Romney, who is having trouble winning over the
conservative voters that Santorum, himself a conservative, is appealing to.

Santorum said Massachusetts benefited from earmarked money from
Washington when Romney was governor.

"Gov. Romney's campaign has been about serially tearing down but not offering any kind of vision about what he wants to do for this country," Santorum said. "He's not going out and talking about his record as governor of Massachusetts. He hides from that record."

Romney had no public appearances Thursday. He issued a statement urging Congress to ban earmarks permanently.

Later in the day, thousands turned out to hear Santorum at a basketball arena on the campus of conservative Oral Roberts University in Tulsa.

Santorum was scheduled to be in Washington on Friday to address the Conservative Political Action Committee's annual gathering.