As unions rallied outside, NSW Treasurer Mike Baird and Ports Minister Duncan Gay spent lunchtime inside the Port Kembla Port Corporation talking up the proposal to senior employees and board members.

The plan to hand the port to a private operator on a long-term lease was unveiled in last month's state budget.

The NSW Government promised that $100 million of the estimated $500 million in proceeds would be spent on infrastructure in the Illawarra.

Existing port operators, domestic superannuation funds and consortiums from Canada, the United Kingdom, Middle East and Asia have since shown strong interest.

When asked if the amount quarantined for the Illawarra would be boosted should a bidding war produce a better than expected price, Mr Baird said $100 million was a "fair amount".

"'That's the allocation we have put into it [and] we think that is a fair amount for this region," he said.

"Obviously, part of the rationale for the transaction is not just to help with infrastructure here in the Illawarra but across the state.

"So it's about balancing [the needs] of those two and we think that [$100 million] is a fair proposal."

Mr Baird and Mr Gay denied a long-term lease threatened the port's growth.

But unions are worried any change threatens jobs and believe the port's strong financial position means its public ownership should be retained.

"We're being sold out," said Maritime Union of Australia Southern NSW Branch deputy secretary Scott Carter.

"The community's asset will be flogged off for a gain by big business.

"The port is not struggling, it is going ahead, we are expanding, we are making profits [so] why privatise it to big business?"

About 80 people attended yesterday's rally. More are planned.

Mr Baird and Mr Gay said they were prepared to meet with concerned union leaders.

"They [the rally participants] remind Mike and I, if we ever needed reminding, there are people involved here, there are jobs involved here, we need to be careful about those things and we definitely will be," Mr Gay said.

What parts of the port are leased and what impact it will have on employment will be outlined by a scoping study currently under way, he added.

What projects the $100 million would be spent on won't be determined until later this year.