A statement from the CWU said the negotiation period had been extended until September 9 "in order to resolve all issues in dispute".
Last month CWU called off planned strike action following a meeting attended by Royal Mail chairman Allan Leighton and chief executive Adam Crozier, which was monitored by the Trade Union Council.
The present dispute stems from CWU members rejecting Royal Mail's 2.5% pay rise offer and plans to modernise, which the union claims could result in an "unacceptable number of job cuts".
The CWU orchestrated a two-week programme of one-day strikes from July 25, as the disagreement with Royal Mail intensified, and what the union described as a lack of "progressive discussions".
The decision to suspend further strike action until September 9 raises hopes that the dispute between CWU and Royal Mail could be resolved, but it is still unclear whether the two parties are nearer to finalising a deal.