Incitec Pivot has signalled that its struggling Gibson Island fertiliser plant may continue operating beyond the expiry of a crucial gas contract in September, despite an expected $49 million rise in the cost of gas.

The optimistic tone toward Gibson Island, which employs about 1500 people on the outskirts of Brisbane and is politically sensitive, came as Incitec reported a weaker-than-expected $147.1 million underlying profit for the six months to March 31.