Cuban President Raul Castro told President Obama in an exchange of letters that the Cuban government — known for its routine mass arrests of political dissidents — is suddenly behind ideas like "human rights and fundamental freedoms for all."

Castro and Obama exchanged letters as part of the process of normalizing relations. In each, the two leaders stressed their commitment to the principles in the United Nations Charter and international law.

Castro's letter said Cuba is "likewise inspired" by these principles, which include the concepts of friendly relations "based on respect for the principles of equal rights and self-determination of peoples," and "promoting and encouraging respect for human rights and fundamental freedoms for all."

It's a line that many skeptics in Congress were doubting even before Castro wrote it down. Most Republicans and many Democrats have said it's a mistake for Obama to open relations with Cuba, precisely because the Cuban government has failed to undertake any new commitments in the areas of political rights and freedoms.

Even in recent months, Cuba has arrested dozens of pro-democracy protestors. In December, Cuba seemed to indicate a break in its behavior when it agreed to release 53 prisoners — that was done as a token of goodwill, and many saw it as a move to help secure Obama's agreement to push for normalized relations.

But reports quickly surfaced that some dissidents were re-arrested soon after they were released. And in February, Cuba had arrested dozens of additional dissidents, a fact some Democrats ignored while they were touring the island nation in anticipation of a diplomatic breakthrough.

Cuban-American members of Congress like Rep. Ileana Ros-Lehtinen, R-Fla., say Cuba continues to make these arrests, and say the U.S. hasn't done enough to ensure the promise in Castro's letter is held.

Wednesday afternoon, Ros-Lehtinen said in a tweet that re-opening embassies at this point is "yet another concessions 2 regime that continues arbitrary arrests."

In another, she said the embassy "will not help our #NationalSecurity nor bring #freedom to the #Cuban people."

Obama's letter to Castro made the same reference to the principles of the UN Charter, and called the agreement to open embassies on July 20 an "important step forward in the process of normalizing relations."

Read both letters here:

Castro to Obama

Obama to Castro