Uzbekistan's parliament has approved Prime Minister Shavkat Mirziyoyev, 59, as interim president.
The move is a clear sign he will become the long-term successor to strongman Islam Karimov, who died last week.
Under the constitution, Senate leader Nigmatilla Yuldashev should have taken the interim role but reportedly declined.
Parliament also confirmed a presidential election will be held within three months.
The BBC's Abdujalil Abdurasulov says the election may well be just a formality - as it was during President Karimov's rule.
Karimov, 78, died after a stroke and was buried at the weekend in his home city of Samarkand.
Karimov, one of Asia's most autocratic leaders, had ruled for 27 years, and was accused by human rights groups of harshly repressing dissent.
Mr Mirziyoyev, PM since 2003, was the mourner-in-chief at the funeral service, and earlier this week met Russian President Vladimir Putin.
Shavkat Mirziyoyev: The right-hand man
- Born 24 July 1957. Reports vary of his place of birth, some saying it was in Tajikistan's Urateppa region and his family moved to Uzbekistan in the 1960s
- Degree in mechanical engineering
- Governor of Jizzakh region (1996) and Samarkand region (2001)
- Appointed PM in 2003
- Described as Karimov's right-hand man. A tough, ambitious figure rarely seen on TV
- Accused by rights groups of using child and forced labour to harvest cotton
- Source: BBC Monitoring
Mr Yuldashev is a low-profile figure and Reuters quoted an Uzbek source as saying the Senate head had declined the interim role because of his lack of experience.
Karimov's death had sparked speculation of a battle for succession. Mr Mirziyoyev's deputy, Rustam Azimov, had also been seen as a key player.
But Kamoliddin Rabbimov, an Uzbek political analyst who used to work in the presidential administration before fleeing to France, told the BBC that Mr Mirziyoyev held more "state resources".
"He has been at this job for 13 years and appointed his people to key positions all around the country," Mr Rabbimov said.
However, political analyst Andrey Saidov said Mr Mirziyoyev's rise to the presidency was not certain as "he is not that popular among the people".
News of Karimov's death was finally confirmed last Friday following days of rumours.
Karimov had often justified his strong-arm tactics by highlighting the danger from Islamist militancy in the mainly Muslim country, which borders Afghanistan.
A United Nations report described the use of torture under Mr Karimov as "systematic".
During a crackdown in the eastern city of Andijan in 2005, hundreds of people were killed.