A tourist takes a selfie next to placards placed by anti-Brexit supporters stand opposite the Houses of Parliament in London. Picture: Matt Dunham/AP

London - British Prime Minister Theresa May will request a short delay to Brexit in a letter to the European Union on Wednesday, Sky cited an unidentified senior government source as saying.

The delay, nearly three years since the United Kingdom voted to leave the European Union, leaves the Brexit divorce uncertain with options including leaving with May's deal, a longer delay, a disruptive exit, or even another referendum.

Just 9 days before the March 29 exit date that May set two years ago by serving the formal Article 50 divorce papers, May is due to write to European Council President Donald Tusk to ask for a delay.

But the ultimate length of the delay was unclear amid the political chaos in London. May had warned that if parliament did not ratify her deal, she would ask to delay beyond June 30, a step that Brexit's advocates fear would endanger the entire divorce.