The new president was supposed to take over yesterday, but rivals Abdullah Abdullah and Ashraf Ghani, as part of a US-brokered deal, must form a government of national unity and co-operate on an audit of all eight million votes that were cast to eliminate concern about widespread electoral fraud.
Afghanistan has been in a state of crisis since the disputed first round of the presidential election in April and the continuing stand-off has dashed hopes for a smooth transition of power from President Hamid Karzai, who has run the country since 2001.
Mr Karzai had earlier said the new leader would take over yesterday, but a spokesman for the president said yesterday that this was never set as the inauguration date.
The Independent Election Commission is still examining votes cast in a second-round run-off held under UN supervision on June 14.
In particular, the commission is due to begin throwing out, or "invalidating", ballots deemed fraudulent in an audit of all eight million votes cast, organised as part of a deal to resolve the stand-off.
A new inauguration target date has now been set for September 2.