Democratic Sen. Gary Peters told CNBC on Wednesday that he's seeing broad bipartisan opposition to President Donald Trump's proposed tariffs on Mexican goods.

Trump warned last week that he would impose a 5% tariff on Mexican imports, starting June 10, if Mexico doesn't take action to "reduce or eliminate the number of illegal aliens" crossing the U.S. border. Trump's tariffs, if enacted, would go up incrementally over several months to a 25% rate by October.

As the Monday deadline nears without a resolution, senators on both sides of the aisle are starting to become worried about how the duties will impact their constituents.

"My Republican counterparts are very concerned about these tariffs," said Peters, ranking member of the Homeland Security Committee. He also serves on the Armed Services, Commerce, and Joint Economic committees. The Michigan Democrat, whose state includes the U.S. auto epicenter of Detroit, is up for reelection in 2020.

GOP senators have broadly opposed the tariffs on Mexico and have signaled they would likely vote against Trump's move. Many Republican lawmakers had a lunch Tuesday where several echoed Peters' statements.

"If the outcome of this game of chicken is massive new tariffs that destroy jobs in Texas and across America that would be a terrible outcome," Republican Sen. Ted Cruz from Texas told reporters.

Republican Sen. Rob Portman of Ohio told CNBC on Tuesday that Trump should not follow through with his Mexico tariffs. Portman, who was U.S. trade representative during George W. Bush's administration, said the president does not need to force Mexico's hand because experts would say that Mexico has been doing more than it has ever done to curb migrants from illegally entering the U.S.

During his visit to the U.K., Trump said Tuesday, "I think it's more likely that the tariffs go on" against Mexico. He also said he did not think GOP senators would revolt.

Meanwhile, Peters argued that Trump's Mexico tariff proposal does little to address the illegal flow of migrants to the U.S., and it will only hurt workers in American states.

"This does not make sense," he said in an interview on "Squawk Box." "This is a separate policy issue. It certainly goes down a very slippery slope."

Peters is especially concerned with how the proposed tariffs will impact the automotive industry, as several U.S.-based automakers have major production facilities in Mexico.

Immediately after Trump's Mexico tariff threat, shares of General Motors, Fiat Chrysler and Ford all declined, as they all have billions of dollars at stake.

"It would hit Michigan pretty hard," said Peters.