WASHINGTON, Feb. 4 -- The White House was cautious on Wednesday in its comments on the Jordanian government's retaliatory execution of two Iraqi extremists after the Islamic State (IS) released a video purporting to show IS burning alive a Jordanian pilot hostage.

"These were individuals who were sentenced to death and were serving time on death row," said White House spokesman Josh Earnest at the daily briefing. "For questions about the circumstance of their confinement or the decision to move forward on the execution, I'd refer you to Jordanian authorities who can provide a great deal more insight into the Jordanian justice system."

IS militants released a video on Tuesday purporting to show the Jordanian pilot Moaz al-Kasasbeh captured last December being burned alive in a cage, just days after the militants beheaded a Japanese journalist.

The Jordanian government said it has already confirmed the man burned to death was Kasasbeh and vowed an "earth-shaking" response.

Hours after the Jordanians pledged to "retaliate", Jordan executed Sajida al-Rishawi, the female suicide bomber asked for by the IS in a previous proposal to swap prisoners, the state-run Petra news agency reported Wednesday. Another al-Qaeda prisoner, Ziad al-Karbouly, was also hanged to death on the same day, according to the report.

After the executions, Federica Mogherini, the European Union ( EU) high representative for foreign affairs and security policy, said in a statement that Brussels stood by the Jordanians but criticized the Jordanians for using capital punishment as a deterrent.

Earnest refused to comment on whether the White House supports using the death penalty as a form of revenge, saying the United States continued to welcome Jordan's commitment to fighting against IS.

Meanwhile, the Senate Armed Services Committee on Wednesday pressed the Obama administration to move swiftly to increase military assistance to Jordan specifically by giving them more weapons.

In a TV interview with CNN on Wednesday, Chairman of the Armed Services Committee John McCain said all 26 members of the committee wrote in a letter to senior officials of Obama's administration to solicit speedy provision of certain types of military equipment to the Jordanians.

"The Armed Services Committee yesterday afternoon met with ( Jordanian) King Abdullah. He needs some types of weapons very badly. He's having trouble getting those weapons. We'll be working immediately on trying to achieve that for him," said McCain, criticizing the U.S. State Department for imposing "a huge bureaucratic bottleneck" for the Jordanians to get "some technical types of more sophisticated weaponry".

"We'll be looking at legislation that we could pass rapidly through both houses of Congress," said McCain.

Earnest said he was not aware of King Abdullah requesting more U.S. military support during his meeting with Obama on Tuesday night before cutting short his U.S. trip to return home. He said that the White House would consider the possible legislation from Congress, stressing that it should be in accordance with Jordan's specific request.