WASHINGTON (Reuters) - A U.S. Republican lawmaker on Thursday issued a second subpoena for Secretary of State John Kerry to testify before Congress this month about the 2012 attacks on U.S. facilities in Benghazi in which four Americans were killed.

The State Department reacted angrily, saying it was the second time Kerry had been subpoenaed while on foreign travel, and noted the announcement had been made via Twitter. "This is not the way legitimate and responsible oversight is conducted," said State Department spokeswoman Marie Harf.

House of Representatives Oversight and Government Reform Committee Chairman Darrell Issa had earlier issued a subpoena for Kerry to appear on May 21, but lifted that request after the State Department said it would conflict with Kerry's travel schedule. The subpoena issued on Thursday would require him to appear on May 29.

"Absent an assertion of executive privilege, the State Department has a legal obligation to fully and completely comply," Issa said in a statement.

However, Harf's statement indicated the State Department was not keen on the idea. "We will continue to work with the committee to resolve their request, but we have not made arrangements for a hearing date, and we hope to explore with them whether there are witnesses better suited to answer their questions and meet their needs for oversight," Harf said.

Democrats said the subpoena called into question the Republicans' announcement earlier this month of a select committee on Benghazi. It is supposed to bring together the earlier probes by other committees, including Issa's, into one place. Issa was not named to the select panel, which will be led by Republican Representative Trey Gowdy. "The Select Committee is a sign of no confidence in Issa, just as Issa's action today is a sign of a lack of confidence in the Select Committee," Democratic Leader Nancy Pelosi said in a statement.

The Democrats have not decided whether to take part in the select committee to investigate the September 11, 2012, attacks by militants on U.S. facilities in Benghazi that left U.S. Ambassador Chris Stevens and three others dead.

Issa has said he wants Kerry to answer questions about the State Department's response to the investigation, although Kerry was not secretary of state at the time the Benghazi attacks happened; Hillary Clinton was still in charge. She has testified to two committees of Congress about the attacks, but not Issa's.

Republicans accuse the White House of creating a political smokescreen in the aftermath of Benghazi to protect President Barack Obama's 2012 re-election. Democrats accuse Republicans of trying to get political advantage in a congressional election year, and of trying to harm Hillary Clinton's chances of running for president in 2016.