SemGroup on Thursday again rejected the unsolicited $1 billion bid from rival Plains All American Pipeline
, saying the offer does not provide any reasonable basis to begin a discussion.

On Wednesday, Plains urged SemGroup to defer the IPO of a master limited partnership unit and reiterated its $24 a share bid.

SemGroup had rejected the offer in October as soon as it was made public.

SemGroup's shares closed at $28.04 on Wednesday on the New York Stock Exchange. (Reporting by Aftab Ahmed in Bangalore; Editing by Sriraj Kalluvila)