WASHINGTON (Reuters) - President Barack Obama will be accompanied on his historic visit to Cuba this month by up to 20 members of Congress, and is also considering further measures to ease travel and trade restrictions around the time of the visit, U.S. sources said on Monday.

The U.S. flag flies at the U.S. embassy in Havana, Cuba, August 14, 2015. REUTERS/Yander Zamora

Details were being worked out, but congressional sources told Reuters the White House hoped the delegation would include Republicans as well as Obama’s fellow Democrats, to underscore bipartisan support for his moves toward normal relations with the Communist-ruled country.

Republican Senator Jeff Flake of Arizona, who has been one of his party’s leading proponents of easing the embargo restrictions, said there was “a good chance” he would join the trip. A spokesman for Flake later confirmed he would be going.

Congressional aides and sources outside the government who were consulted on the matter said timing was still uncertain, but the administration could roll out more changes to travel, trade and banking rules before or during the March 21-22 visit.

“They will unveil a regulations package as it gets closer to the trip, further easing of travel, and further commerce and trade (changes),” said one person familiar with the discussions.

Obama’s aides are considering regulatory changes to make it easier for individual Americans to visit Cuba as long as they qualify for 12 authorized “people-to-people” categories of travel, the sources said. Until now, most have been allowed to visit Cuba only on group tours or to see family on the island.

The White House is also weighing possible revisions and clarifications of how the dollar can be used in trade with Cuba, a person familiar with the discussions said.

The White House said on Feb. 18 that Obama would visit Havana on March 21 and 22 in another step toward ending decades of animosity between the former Cold War foes. It will be the first visit to Cuba by a sitting U.S. president since 1928.

News of Obama’s trip prompted sharp criticism from some members of the Republican-controlled Congress, where there is strong opposition to normalizing relations with Havana, mostly from Republican lawmakers.

ELECTION COMPLICATIONS

Some Republicans want more normal relations with Cuba, as do most Democrats. But the issue is complicated on Capitol Hill because two senators vying for the 2016 Republican presidential nomination, Ted Cruz and Marco Rubio, both Cuban-Americans, strongly oppose Obama’s policy shift.

Obama said the trip would help accelerate changes in Cuba since he and President Raul Castro announced moves to restore ties in late 2014. Administration officials hope it will give Washington more leverage to make progress on opening business opportunities for U.S. companies.

Opponents say Obama has demanded too little from Havana, particularly in the area of human rights, to end the embargo imposed in 1960. The administration believes that moves to loosen the embargo would help meet its goal of benefiting the Cuban people.

Obama has used his executive powers to ease some trade and travel restrictions since announcing his new Cuba policy 15 months ago. Some major U.S. airlines have begun asking regulators to approve routes to Cuba.

So many lawmakers are expected to make the trip that the White House is arranging a separate aircraft to transport them, congressional aides said.

“As the president has done on past trips, he has invited a group of senators and House members to join him on his upcoming trip to Cuba. Further details on the members’ travel will be available closer to the departure date,” a White House official said on condition of anonymity.

Analysts said establishing U.S.-Cuban business relationships would make it difficult for the next U.S. president to roll back Obama’s policy changes after he leaves office next January, if a Republican opponent of the policy wins the election.

Businessman Donald Trump, the leading Republican candidate, told the Daily Caller in an interview published in September that he supported the Obama administration’s opening with Cuba.

But the embargo cannot be lifted without Congress’ approval and Republicans say that will not happen while Obama is president.