The legendary US singer collected the 'Icon' award at this year's Glamour Awards earlier this week and surprised the crowd by name-checking the X Factor UK champion.
Warwick described Burke as "very special" and "a true star" during her acceptance speech.
"I was stunned and totally overwhelmed. She is a legend and an icon. I only met her last night," Burke is quoted by Metro as saying, following the praise.
The pair duetted for the first time earlier this week at London's Royal Albert Hall as part of a concert to mark World Hunger Day.
Burke's new single 'Let It Go' is available to download now, while her second album Heartbreak on Hold will be released on June 4.
Watch the music video for Alexandra Burke's 'Let It Go' below: