Speaking with reporters after a lunch meeting with state legislators, the incoming governor said he believes the troopers have enough to do already without having to also enforce immigration laws.
"If I have that power, I'm going to rescind that agreement," Patrick, a Democrat, told reporters.
He added: "I do believe I have that power."
The change would mark the second split with the Romney administration in two days. On Wednesday, Patrick said he cannot support a plan to remove tolls on the western portion of the Massachusetts Turnpike because he does not believe it is economically feasible.
On Dec. 13, Gov. Mitt Romney signed an agreement with federal authorities allowing troopers to arrest and seek deportation of suspected illegal aliens they encountered during their normal duties.
Under the terms of the deal with the U.S. Immigration and Customs Enforcement agency, an initial group of 30 troopers was to receive five weeks of specialized training next year, paid by the federal government. Patrick takes office on Jan. 4.
Romney, a potential Republican candidate for president in 2008, said at the time: "The scope of our nation's illegal immigration problem requires us to pursue and implement new solutions wherever possible."
The customs enforcement agency has similar agreements with state agencies in Florida, Alabama and Arizona, and with county correctional agencies in California and North Carolina.
An agency spokesman said 30 other state, county or local agencies have applied to receive the immigration law enforcement authorization and training.
Romney was making political appearances in New Hampshire on Thursday and his office did not immediately respond to a request for comment.
"As I said before, I think the state police have a very big job as it is, without having to add enforcing federal immigration laws on top of it," Patrick said.
On another note, the governor-elect said that he had repaid himself the bulk of the money he put up to seed his campaign. In total, he contributed $348,000 to his committee, but under state campaign finance law, he is eligible to repay himself up to $200,000 from subsequent donations to his committee.
"The campaign, I'm happy to say, has paid all of its debts — including that one," Patrick said.