Senate Majority Leader Mitch McConnell said Thursday that his chamber is unlikely to approve an American ambassador to Cuba, dishing out a quick rebuff to President Barack Obama and his drive to normalize relations with the U.S. neighbor and longtime Cold War foe.

The Kentucky Republican also suggested that the GOP — which controls Congress — would fight Obama administration efforts to fully lift trade and travel restrictions that have limited American commerce and tourism with the communist-led island nation. McConnell said the country was led by "a thuggish regime."

The comments by McConnell came a day after Obama and Cuban President Raul Castro announced that the two nations will open embassies in Havana and Washington July 20 and resume diplomatic relations severed in 1961, the year Obama was born.

McConnell's remarks underscored that despite a push to ease the curbs by U.S. business and agriculture interests and some GOP lawmakers, Republican leaders remain sympathetic to the party's more conservative, anti-Castro voices. House Speaker John Boehner, R-Ohio, and several contenders for the GOP's 2016 presidential nomination criticized Obama's moves shortly after they were announced Wednesday.

"You would think that the normalization of relations with Cuba would be accompanied by some modification of their behavior," McConnell said Thursday at Commerce Lexington, the chamber of commerce for Lexington, Kentucky. Instead, he called the country "a police state" and "a haven for criminals" wanted in the U.S.

"I don't see any evidence at all that they are going to change their behavior. So I doubt if we'll confirm an ambassador, they probably don't need one," McConnell said.

He added, "Some of their restrictions on Cuba would require legislation to lift, and we're going to resist that."

Though Obama has not nominated an ambassador for Cuba yet, the current top U.S. diplomat there, Jeffrey DeLaurentis, was expected to be considered for the post.

Labeling the moment "a choice between the future and the past," Obama on Wednesday revealed the latest steps in a half-year of rapid-fire improvements in relations between two nations that lie 90 miles apart but have spent nearly six decades separated by light years diplomatically and economically.

Obama also asked Congress to lift the economic and travel embargoes that the U.S. has used for decades to try forcing Cuba's leaders toward democracy. Obama has partly eased those restrictions on his own, but even before McConnell's comments Thursday, longtime opposition from many Republicans and some Democrats had made it unlikely that lawmakers will fully revoke the bans quickly.

When President Dwight Eisenhower broke relations in 1961 with the communist regime of Raul's brother, Fidel Castro, it set the tone for decades of Cold War hostility that included failed U.S.-backed efforts to overthrow the island nation's leaders.

Besides McConnell and Boehner, denunciations also have come from several 2016 GOP presidential hopefuls, including former Florida Gov. Jeb Bush and Cuban-American Republican Sens. Marco Rubio of Florida and Ted Cruz of Texas. In a typical comment, Bush said warming relations should "advance the cause of human rights and freedom for the Cuban people" and said the administration's moves were "failing this test."

Rubio and Cruz each said they would try blocking any Obama effort to win Senate confirmation of an ambassador to Havana.

While Republicans are likely to strongly oppose large expenditures to improve relations with Cuba, the administration may be able to use smaller amounts to buttress its diplomatic presence there.

Obama has requested $6 million to improve the current, lower-level U.S. outpost there. Congressional aides said that even without specific approval from lawmakers, the State Department could well access that money because agencies can unilaterally shift relatively small amounts among their budget accounts.

Though it's not yet law, the GOP-led House Appropriations Committee approved foreign aid legislation last month barring work on a U.S. Embassy in Cuba unless Obama certifies that Havana is meeting the terms of a 1996 statute aimed at fostering democracy in Cuba. That includes extraditing people wanted in the U.S. for crimes.

The Republican-controlled Senate Appropriations Committee plans to write its version of the aid measure next week.

The two countries' surprise revelation last December that they would move toward normal relations has been followed by other steps. The U.S. has lifted some travel curbs on Americans and began permitting U.S. companies to export telephones and computers to Cuba, and has removed Cuba from the list of countries sponsoring terrorism.

Yet divisions remain.

The U.S. remains focused on Cuba's reputed human rights violations. Cuba wants an end to the U.S. economic embargo, the return of the U.S. military base at Guantanamo Bay and a halt to U.S. broadcasts aimed at the island.