(AFP) - Kenya's highest court began Tuesday weighing a legal bid to revive government plans to shake up the country's political system, just months ahead of crucial elections.

The Supreme Court ruling on the proposed constitutional changes, expected after three days of hearings this week, may have major consequences for the August 9 presidential and parliamentary polls.

The government is seeking to overturn court rulings that had dealt a blow to President Uhuru Kenyatta and his allies by rejecting the reforms and the way they were introduced as unconstitutional.

The so-called Building Bridges Initiative (BBI) aims to expand the executive and overturn the winner-takes-all electoral system blamed for frequent explosions of poll-related violence in the East African nation.

But Kenyatta's detractors see it as little more than a naked grab for power by a two-term president who cannot run a third time, with the BBI potentially allowing him to assume a new post of prime minister.

- 'Freedom to make decisions' -

The BBI was drawn up following a rapprochement between Kenyatta and his erstwhile opponent Raila Odinga and a famous handshake between the two men after post-election fighting in 2017 left dozens of people dead.

The proposed amendments to the 2010 constitution were approved by parliament in May last year and were then due to be put to a referendum.

But just two days later, the Nairobi High Court ruled they were illegal as the president did not have the right to initiate the process.

Kenya's Court of Appeal in August upheld that view and said Kenyatta could even be sued in a civil court for launching the process.

Kenyatta's lawyer Karori Kamau insisted at Tuesday's hearing that the law gives the president immunity from prosecution or civil action while he is in office.

"It is necessary that the president has decisional freedom, to make decisions that are key and important to safeguard the interest of the country," he added.

Some analysts say that even if the Supreme Court's seven-member panel sides with government and allows the proposals to be put to a public vote, there will probably not be time to hold a referendum before the August election.

With its diverse population and large ethnic voting blocs, Kenya -- a country of nearly 50 million -- has long suffered politically-motivated communal violence around election time, notably after a 2007 poll when more than 1,100 people died.

- 'Job promises' -

The East African economic powerhouse on Monday began a second round of voter registration, hoping to attract six million new voters, after a similar exercise late last year was blighted by apathy.

BBI's supporters argue the project would improve fairness in the electoral system and help curb unrest, but critics warn it could undermine the country's democratic institutions while creating more opportunities for patronage and corruption.

The reforms called for the creation of the posts of prime minister and two deputies, as well as an official opposition leader, and the expansion of parliament with 70 new constituencies.

"If the Supreme Court overturns the lower courts on (an) expanded executive, top job promises will take centre stage as campaign strategies and might affect the vote outcome," Nairobi-based US International University lecturer Macharia Munene told AFP.

Odinga, who was the face of Kenya's opposition for decades, announced in December he would make his fifth run for the presidency.

The 77-year-old veteran politician's campaign got a boost on Monday when he won the endorsement of at least 30 of Kenya's 47 county governors -- compared to 10 for his rival, Deputy President William Ruto.

The presidential vote is widely seen as a two-horse race between Odinga and Ruto, whom Kenyatta had initially anointed as his successor.

But Ruto, 55, has been frozen out since Odinga's 2018 pact with Kenyatta, and he is vehemently opposed to the BBI.

© Agence France-Presse