The couple have reportedly put forward a possible date of April 28 for their nuptials and are waiting for it to be cleared by Downing Street and the royal family.
An announcement is now expected at the beginning of next week.
However insiders have said the Liberal Democratic Party might force the date to be scrapped amid fears a ceremony at the end of April would infringe on coverage of the voting system referendum three days later on May 1.
Royal aides have revealed the couple who have been dating for almost eight years are both desperate to get the wedding underway.
One royal insider told Britain's Daily Mail newspaper: "Kate and William both view this process rather like tooth extraction. They want to get back to a life of relative normality as soon as possible to 'get it over with and get back to our quiet life', which is sweet but unrealistic."
Another source added: "They know what they want."