One year after Congress approved a controversial plan to extend the nation’s debt ceiling, Republicans are stepping up their campaign to repeal a major part of the law.

They’re worried about a part of the measure called “sequester,” a requirement that spending for some federal government programs be slashed starting in 2013 once a “supercommittee” of Congress failed to compromise on $1 trillion in deficit reductions last fall.

The law requires that more than $100 billion be sequestered — or automatically cut — in January.

GOP officeholders and candidates, however, aren’t worried about all the automatic reductions. They’re concerned that more than $50 billion in cuts will come from the Defense Department, saying that will threaten national security and tens of thousands of defense-related private-sector jobs.

They’re pushing to rewrite that part of the law.

“It was bad policy to put our national defense at risk, all dependent on this supercommittee,” U.S. Rep. Vicky Hartzler, a Republican, said after a campaign stop in Belton, part of her 4th District. “It will hollow out our military.”

But Democrats have resisted any significant changes to the defense sequester requirements. They contend that Republicans can restore the cuts to defense and other programs if they are willing to consider tax increases on wealthier Americans to battle the deficit.

And they argue that substantial cuts to other government services shouldn’t go forward while defense spending is restored.

“I unequivocally support well-examined and necessary funding for the military,” said U.S. Rep. Emanuel Cleaver. “We must not, however, haphazardly slash programs that assist, for instance, education and children living in poverty.”

The debate over the defense sequester is spreading nationally.

House Republicans and White House officials squabbled angrily over it in a tense hearing Wednesday, each side blaming the other for the looming cuts.

Last week, three GOP senators — led by 2008 presidential candidate John McCain — traveled along the East Coast urging voters to help them overturn the automatic defense cuts next year.

Senate Democrats have responded by deferring votes on lifting the sequester. The spending cuts are supposed to hurt, they say, as an incentive to force compromise on deficit reduction.

The issue will be hotly debated in campaigns this fall, in part because the sequester could cost civilian jobs related to Defense Department spending.

More than 65,000 civilian jobs in Missouri are tied to the aerospace and defense industries, according to a 2011 study by Deloitte, an auditing firm. State officials think the number is even higher.

The government spent more than $9 billion on defense-related contracts in Missouri in 2011, according to a database at GovernmentContractsWon.com.

Aerospace and defense-related employment in Kansas affects more than 100,000 people, the Deloitte study found, largely because of Wichita’s role in aviation.

Defense employment creates “a lot of jobs,” agreed U.S. Sen. Roy Blunt, a Missouri Republican, adding that both political parties share blame for the budget impasse.

The House Armed Services Committee, which counts Hartzler as a member, says Missouri would be among the 10 states hardest hit by a full defense sequester. Overall, the committee’s Republicans claim, the sequester could cost 1 million private-sector jobs, adding to the nation’s stubbornly high unemployment rate.