The prime minister of Solomon Islands has signed the Melanesian Free Trade Agreement making his country the first Melanesian Spearhead Group member to do so.
Only two MSG member countries need sign the agreement for it to come into effect.
The sub-regional trade deal is an expansion of former agreemens between Solomon Islands, Fiji, Papua New Guinea and Vanuatu.
It covers trade in services, investment and labour mobility.
During the signing on Friday Manasseh Sogavare said the sub-regional trade deal was one of the answers to improving the economies of Melanesian countries.
Mr Sogavare also said it was strategically important to conclude the signing process in light of Australia and New Zealand also moving towards completing the regional trade deal with Pacific island countries known as PACER-Plus.
The MSG's deputy director general Molean Kilepak said the next countries expected to sign would be Fiji and Papua New Guinea followed by Vanuatu.