Lawmakers attending Friday's opening of the U.S. embassy in Havana have been some of the biggest supporters of shoring up relations with the island nation and will continue to play a major role in pushing through legislation to lift the trade embargo and travel ban.

"I just can't imagine we are going to get to the point of getting the embargo lifted without embassy functioning," Sen. Amy Klobuchar told CQ on Thursday.

The Minnesota Democrat introduced legislation (S 491) in February to lift the embargo. Arizona Sen. Jeff Flake, who will be in Cuba with Klobuchar on Friday, co-sponsored the bill and has been one of President Barack Obama's leading Republican advocates on Capitol Hill.

Flake, who sits on the Foreign Relations Committee, introduced a measure in January (S 299) to end the travel ban.

The senators, who are accompanying Secretary of State John Kerry, will be joined on the trip by Barbara Boxer, D-Calif., Patrick J. Leahy, D-Vt., and Reps. Jim McGovern, D-Mass., Barbara Lee, D-Calif., Steve Cohen, D-Tenn., and Karen Bass, D-Calif.

Lee, who attended the opening of the Cuban embassy in Washington last month, is a co-sponsor of (HR 403), House legislation that would repeal the trade embargo.

"We need to allow Americans to visit Cuba. It's a freedom issue and its also a business opportunity," Cohen told CQ on Thursday.

Fellow lawmakers, including GOP presidential hopeful Marco Rubio, have been critical of the ceremony itself, which will not include any Cuban dissidents.

"This is a new low for President Obama and a slap in the face by this administration to Cuba's courageous democracy activists," the GOP senator from Florida said in a statement Wednesday. "What a pathetic policy President Obama has embarked on that shuns Cuban dissidents like this, yet has welcomed Castro regime officials to the White House."

Kerry said Cuban dissidents would be welcome after he concluded the ceremony, which is fairly small due to the number of people that can physically fit inside the embassy building.

"I will meet with them, and they are invited to the mission at a later time in the day, and we will have a broad cross-section of civil society in Cuba," Kerry said in a TV interview on Wednesday. "But the actual flag-raising ceremony is, first of all, in a fairly confined space; and number two, it's really principally a government-to-government event."

McGovern and others said opening the embassy will be the first step in renewed engagement.

"I think engagement is a better way to be able to make progress on human rights as opposed to isolation and blockades and travel restrictions," McGovern told CQ.

He said pushback from his colleagues would hamper cultivating these ties.

"We are going to have somebody who is an acting ambassador. We can't have a formal ambassador because of people like Sen. Rubio who won't approve one, which I think is stupid to be blunt," he said.

"But the bottom line is, we will have a better opportunity to raise those concerns directly."