TOKYO (AFP) - Japan's SoftBank said on Tuesday that it was raising its bid for US wireless carrier Sprint Nextel Corp as it looks to head off a rival offer with a higher headline figure from Clearwire.

Softbank said in Tokyo it would up its original bid by US$1.5 billion to US$21.6 billion (S$27 billion).

The move came just ahead of the Wednesday meeting of Sprint shareholders, when they are set to vote on the proposed takeover.