According to TMZ, the couple - who announced their engagement last March - were already thought to have tied the knot, but have only applied for the marriage licence this week.
Khalifa and the model were seen on Tuesday (July 2) applying for one at a kiosk at a Los Angeles courthouse.
The news suggests that a wedding is imminent, as the pair now have 90 days to get hitched under the terms of the current licence.
However, no details concerning the forthcoming ceremony have been confirmed.
Back in February, the Black And Yellow rapper and Rose welcomed their first child together, son Sebastian Taylor Thomaz.
They begun dating in 2011 following Amber's well-publicised two-year romance with Kanye West.
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