Myanmar has freed 23 political prisoners, the latest pardon coming just days before President Thein Sein makes a symbolic visit to the United States.

Thein Sein will meet President Barack Obama in the White House on Monday, becoming the first Myanmar leader to visit the US in over decades. The two leaders are expected to talk on how the US can assist Myanmar’s efforts to “develop democracy, address communal and ethnic tensions, and bring economic opportunity to the people,” according to a statement released by the White House.

Warming relations between the two countries, brought by sweeping reforms initiated by a nominally civilian government, has led to the release of hundreds of political prisoners. But Zaw Htay, a senior official in the president’s office, said the release has nothing to do with Thein Sein’s visit to Washington.

Activists cautiously welcomed the latest amnesty and said Myanmar still faces challenges in releasing political prisoners.

Bo Kyi, a former political prisoner and joint-secretary of the Assistance Association for Political Prisoners, said prisoners are routinely released under tight conditions and are vulnerable to re-arrest if they anger authorities.

“The government’s intention is to ease international pressure,” he said. “We are appealing to President Obama to pressure President Thein Sein to release political prisoners unconditionally”.