Palestinian President Mahmoud Abbas has issued new orders for his deputy Hussein Al Sheikh to replace him "in the event of a vacancy".
The decree issued by Mr Abbas, 89, provides for Mr Al Sheikh to "temporarily assume the duties of the President for 90 days". There would then be new elections.
Mr Abbas revoked a previous order under which Rawhi Fattouh, the chairman of the Palestinian National Council, would have temporarily held the office, according to official Palestinian media.
The decision appears to bolster Mr Al Sheikh's position after he was named vice president in April, when the role was created. It comes amid international pressure to reform the Palestinian Authority with a view to one day handing it control of Gaza.
Sunday's declaration aims to "protect the Palestinian political system, safeguard our homeland, ensure its security, and preserve its constitutional institutions", Mr Abbas said. It allows for the acting president's term to be extended if elections cannot be arranged.
"The freedom of the individual, the rule of law, and the promotion of values such as equality, democracy, pluralism, and social justice are the basis of the legitimacy of any ruling system that will lead the country in the next phase of our people's history," Mr Abbas said.
The Palestinian Authority (PA) already exercises limited control over the Israeli-occupied West Bank. But Mr Abbas and his government are widely seen as unpopular. Mr Al Sheikh is regarded as having built a good working relationship with Israel during his years of representing the authority.
Mr Al Sheikh recently held talks with the former UK prime minister Tony Blair on possible future arrangements for the governing of Gaza. The US President Donald Trump's peace plan calls for a Palestinian committee to run services "until such time as the PA has completed its reform programme".
There have long been concerns of a dangerous power vacuum in the event of Mr Abbas, who turns 90 next month, becoming incapacitated. Rival factions of his Fatah party could vie for control of Palestinian institutions, and critics say Mr Abbas has dodged the question for fear of unrest.

