A delay in signing a "crocodile" defence treaty with Papua New Guinea has "no downside", Prime Minister Anthony Albanese says, brushing aside claims it's an embarrassment for Australia.

Mr Albanese left Port Moresby on Wednesday without the hoped-for defence pact after the PNG government's cabinet didn't sign off on the landmark agreement in time.

He and his counterpart James Marape were expected to ratify a mutual defence treaty deepening military co-operation, but only managed a communique laying out the wording of the pact.

It marks the second time in as many weeks that Mr Albanese has failed to wrap up an actively promoted security deal with a Pacific nation amid geostrategic competition, primarily China.

Mr Albanese returned empty-handed from a visit to Vanuatu last week, after fa

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