The pair, who were both convicted then acquitted in the murder of Kercher, a British student, were spotted walking around New York City Tuesday, with Knox's mother trailing behind them, The Mirror, Britain, reported.
The meet-up came shortly after an Italian court ruled Knox, 25, and Sollecito, 29, be retried, saying their 2011 release was full of "deficiencies, contradictions and illogical."
Knox, an American student, declined to answer whether she would return to Italy for the trial.
Sollecito, an Italian, said: "We have everything to do now. We have a lot of planning."
In 2007, Kercher's body was found in her bedroom in the apartment she shared with Knox in Perugia, a central Italian town.
All three were convicted and sentenced to jail time, but Knox and Sollecito were released four years later when a judge ruled prosecutors failed to prove their guilt.