Abdullah claims that fraud cheated him of victory in the June 14 election, and fears have risen of a return to unrest of the 1990s civil war after his supporters called on him to form a "parallel government".
As tensions threatened to boil over, the United States brokered a deal between Abdullah and his rival Ashraf Ghani in which they agreed to an audit of all eight million votes and the formation of a post-election national unity government.
"Our patience is running out, any announcement of results made by the fraudulent election commission will be rejected by us," Sancharaki told reporters.
"We are setting this deadline -- that if tomorrow our logical demands of transparent auditing and an honest political process are not met, we will completely boycott the whole process."
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Last week Abdullah pulled out of the audit, but had said difficult negotiations on the national unity government were still under way.
"The problem is that (Abdullah's) team wants more authority for the chief executive, for him to be like a prime minister," Tahir Zaheer, a spokesman for the Ghani campaign, told AFP, denying negotiations had already collapsed.
"These threats of an ultimatum will not change anything, there are no logic in them. They have to be realistic."
Abdullah won the first-round election in April out of a field of eight candidates, but preliminary results from the June run-off showed that he was far behind Ghani.
Many of Ghani's supporters are Pashtuns in the south and east, while Abdullah's loyalists are Tajiks and other northern groups.