A spokesman for the 88-year-old senator from New Jersey tells The Star-Ledger that Lautenberg has "personal plans" for Tuesday.
He plans to arrive at the convention in Charlotte, N.C. on Wednesday.
At least two well-known New Jersey Democrats have explored running for Lautenberg's seat in 2014. One is state Senate President Stephen Sweeney. The other is Newark Mayor Cory Booker, who is scheduled to speak at the convention Tuesday night.
Lautenberg has not announced any plans to step aside.