The Gloucester captain and No. 8 boosts a forward contingent which has lost through injury Ospreys lock Alun Wyn Jones and, through suspension, Blues back row Andy Powell.
But the four-times capped Delve, who returns to the international scene for the first time since 2008, will also provide cover for Wales captain Ryan Jones whose calf problems have been well documented during the current campaign.
"We are expecting Ryan to be fine," said Wales assistant coach Neil Jenkins.
"But we have called on Gareth to boost the squad numbers in the forwards and provide cover in that back row area."