Qatar, which hosts the largest U.S. air base in the Middle East, summoned the U.S. ambassador on Thursday over a video posted online that showed American soldiers laughing in front of the nation's flag.

The Qatari foreign ministry said it had "summoned the American ambassador ... over a video which was recently circulated on social media. She was asked for an explanation of the contents of that video."

The clip shows two uniformed U.S. soldiers, a man and a woman, speaking into camera and joking in front of a U.S. and a Qatari flag.

U.S. Ambassador Dana Shell Smith who, according to a ministry official, met Qatari assistant foreign minister Sultan Al Muraikhi on Thursday, said on Twitter that she had apologised.

"The U.S. military command was sent to investigate this incident and disciplinary action will be taken," Smith wrote on her Twitter account, responding to a tweet from a Qatari national.

"Rest assured that these soldiers made fun of themselves and not of the state of Qatar," Shell said in another tweet, written in Arabic.

With enormous natural gas reserves that make it one of the world's wealthiest countries, Qatar is home to the U.S. air base Al Udeid where around 10,000 military personnel are stationed, and is one of Washington's main Arab allies.