WASHINGTON — The head of US intelligence intends to declassify parts of a video showing the deadly attack on the US mission in Benghazi, Libya, according to a congressman briefed by him on Friday.

Lawmakers in closed-door intelligence briefings this week saw a 45-minute video that included images from an unmanned drone over the US consulate in Benghazi, where a September 11 attack led to the deaths of four Americans.

Republican Howard McKeon, chairman of the House Armed Service Committee, told reporters that Director of National Intelligence James Clapper plans "to declassify it to get it out so that everybody in the public can see it.

"He said he thinks that they will be able to do that. I'm hopeful that the sooner the better," he said.

Republicans and Democrats have sparred for weeks over exactly what happened in the Benghazi attack, with Republicans irate over the Obama administration's shifting account of the incident.

At first US officials said the attack was the result of a "spontaneous" protest about an anti-Islam video made in the United States, then eventually acknowledged it was a terrorist assault.

Release of the video could shed further light on the incident.

Democrat Dutch Ruppersberger said that of the data on the Benghazi incident shared with lawmakers this week, "the most important thing was the real time information that we got yesterday, seeing the film on the first attack.

"That was important. That clarified a lot of issues," he said.