The move should ensure a unity government will once again administer both the West Bank and Gaza after the rift caused by militant group Hamas' takeover of the Gaza Strip in 2007.
The Fatah official stressed that President Mahmoud Abbas instructed the delegation not to return without a reconciliation deal.
Al-Ahmad, who is also the head of Fatah delegation for the Cairo talks, said what was agreed upon two weeks ago under the auspices of Egypt is empowering the legitimate government to operate in accordance with its powers in accordance with the Basic Law in effect in the West Bank.
The agreement stipulates that legislative, presidential and national council elections should be conducted within one year of its signing, though details of the reconciliation deal have not yet been made public.
Fatah official said the Palestinian president is planning to visit Gaza Strip within a month as part of the unity bid in what would be his first visit in a decade.More news: Supreme Court dismisses case against Trump's expired travel ban
Israel viewed the Palestinian accord warily, saying it must abide by previous worldwide agreements and terms set out by the Quartet of Middle East peace mediators - including the recognition of Israel and the disarming of Hamas.
Hamas suggested in a new political manifesto earlier this year that it might consider a state in pre-1967 lines as an interim option, but also endorses an Islamic state in historic Palestine, including what is now Israel.
Faced with increasing isolation and a severe electricity shortage, Hamas has reached out to Cairo for help, hoping to have the Rafah border with Egypt opened.
A major sticking point has been the Hamas military wing and its arsenal, which Hamas has said is not up for discussion.
Israeli Prime Minister Benjamin Netanyahu wrote on Facebook that any reconciliation deal must make Hamas disarm and "end its war to destroy Israel". Israel and Egypt imposed a blockade on the territory, severely restricting Palestinians from leaving the territory and goods from entering.