Gov. Chris Christie of New Jersey vetoed a state budget on Monday that would have paid the pension contributions he promised in signature legislation three years ago, risking a rebuke from a court that last week said he had a contractual obligation to make them.

With only hours left to approve a budget before the new fiscal year starts on Tuesday, Mr. Christie said he would pay only $681 million toward the pension obligations for state employees in that year, instead of the $2.25 billion he promised in 2011 and again in his budget proposal in February.

He used his line-item veto to cut the pension payments, as well as tax increases that would have paid for them, from a budget sent to him by the Democratic Legislature last week.

Mr. Christie’s reputation as a rising star in the Republican Party was built on the pension agreements in 2010 and 2011. The next year, he told the Republican National Convention that he had fixed the problem of rising costs for state employees — a problem that bedevils states across the country.