The 'Rehab' singer - who was previously denied a US visa for possessing cannabis and assaulting a fan - wants to reaffirm her commitment to her former spouse but needs to get the all-clear from authorities before they can fly out to plan the ceremony.
The couple - who reconciled earlier this year, months after divorcing - originally married in a surprise ceremony in Miami, in May 2007 and although the pair are planning a similar laid-back approach to their nuptials, have opted for a different US location because the singer is scared returning to Florida could be disastrous for their relationship.
A source said: "They will definitely be getting married and have agreed on Las Vegas. Amy doesn't want a traditional ceremony and wants it to be similar to their first wedding.
"She chose not to marry in Miami again because she thinks it could be a bad omen. She can't stop talking to people about their future together."
Their wedding plans come after the 26-year-old star has bought a new house in Camden, North London, which she has been referring to as "our new home" and hopes to raise a family there once Blake, 27, is allowed to return to the city after completing a rehabilitation programme in Sheffield, North England.
The source added to The Sun newspaper: "Amy and Blake have cleaned up their act and want a fresh start.
"She picked the new place because it is big enough to be a family home."
It was recently claimed that Blake has asked Amy to seek help for her alcohol abuse before they marry again.
A source said: "Amy is always telling Blake she wants to get married again but he's saying not until she cleans up her act."