The person spoke to The Associated Press on condition of anonymity Sunday night because contracts can't be completed until the moratorium on NBA free agency ends Thursday. ESPN first reported the contract discussions.
Casspi has averaged 7.9 points, 3.9 rebounds and 20.8 minutes per game in six seasons. The Kings drafted the Israeli-born Casspi 23rd overall in 2009.
He spent his first two years with Sacramento before playing two seasons with Cleveland and one with Houston. The Kings signed Casspi again last summer after he was waived by New Orleans.
Casspi had several big games after George Karl took over as coach in February.