Kerry slapped with a subpoena by Congress over Benghazi

US Secretary of State John Kerry was slapped with a subpoena on Friday by Congress's main oversight panel. The House Government Oversight Committee is demanding Kerry testify about US President Barack Obama’s administration’s response to the deadly 2012 attack on its embassy in Benghazi, Libya.

Committee chairman Darrell Issa announced the subpoena in a tweet, saying Kerry would be required to testify on 21 May.

"It is because the State Department has failed to meet its legal obligations that I have issued a subpoena to Secretary Kerry," Issa wrote.

House Republican Speaker John Boehner also said on Friday that he is establishing a select committee to investigate the deadly 2012 attack on the US mission in Benghazi, Libya.

The moves come after a conservative group on Wednesday published a White House email it had obtained via a legal challenge and which critics said shows an attempt to put a political spin on the assault.

In the email three days after the 11 September 2012 assault, Obama's deputy national security advisor Ben Rhodes told Susan Rice - at the time US envoy to the United Nations - to blame the attack on local anger in Benghazi over an anti-Muslim Internet video.

It has since become clear that the attack on the mission, which cost the lives of four Americans, including ambassador Chris Stevens, was planned by armed militants.

Republicans including Issa, Boehner and Senator Lindsey Graham have argued that the White House misled Americans about what happened, particularly in the weeks after the attack, which occurred at the height of the US presidential race won by incumbent Barack Obama.

Issa demanded administration officials release any and all documents related to Benghazi.

"The State Department is not entitled to delay responsive materials because it is embarrassing or implicates senior officials," Issa wrote.

The dual announcement of the committee and subpoena suggest that Boehner has finally relented to his party's right flank, which has long pressed for stronger action to probe the attack, and that the Republicans are now determined to elevate investigations to a new level. The bold moves also come a week after Kerry caused major controversy by saying Israel risked becoming an "apartheid" state, a statement that prompted some Republicans to call for his resignation. 

"These revelations compel the House to take every possible action to ensure the American people have the truth about the terrorist attack on our consulate," Boehner said in a statement.

"In light of these new developments, the House will vote to establish a new select committee to investigate the attack, provide the necessary accountability, and ensure justice is finally served."

The White House has stayed firm on the issue, slamming the Republicans for trying to "politicise a tragedy" and uncover a conspiracy where none exists.

The incident has already been investigated "ad nauseum, by multiple committees" and an internal Accountability Review Board,” State Department spokeswoman Marie Harf said.

Harf scoffed at the suggestions by some extreme Republican politicians that the Rhodes email was a smoking gun in the administration's Benghazi account.

"It doesn't change the narrative" of what happened, Harf said of the email, adding that the administration had provided tens of thousands of documents to lawmakers on a rolling basis.

"I am confident that what the Republicans allege, that there was some attempt by this administration to cover up or spin what happened, is 100 percent false," she added.