SABAC, Serbia, July 29 (Reuters) - Thousands rallied on Monday...

SABAC, Serbia, July 29 (Reuters) - Thousands rallied on Monday in the Serbian city of Sabac to protest the Rio Tinto RIO.L (RIO) lithium project, over fears it could cause environmental harm.

Lithium, which is regarded as a critical material by the European Union and the United States, is used in batteries for electric vehicles and mobile devices.

Rio Tinto aims to start mining in Serbia's lush western region of Jadar, but its plans have met with fierce opposition. Last week, protests against the mine took place in several towns across the country.

Protests on Monday were also held in three other towns in central Serbia. More rallies were expected in the coming days.

Protesters in Sabac, about 50 kilometres northeast of the designated mine site, demanded that it be cancelled.

"We cannot live without clean air and water, but we can live without lithium batteries and electric cars," Biljana Stepanovic, of the Proglas (Proclamation) rights organisation told the crowd.

Earlier this month, Serbia reinstated Rio Tinto's license to develop what would be Europe's biggest lithium mine, more than two years after it was annulled due to protests by environmental groups.

On July 19, President Aleksandar Vucic, German Chancellor Olaf Scholz and EU energy chief Maros Sefcovic signed a deal over access to raw materials mined in Serbia.

Last week, Vucic said a referendum on the project will be organised by the end of 2025.

At the rally in Sabac, protesters dismissed assurances by Scholz that the Jadar project would only proceed if it is in compliance with EU environmental standards.

"With this project there will be no future. ... This means death for the people," said Sinisa Todorovic, 52, a salesman.

Various green groups have previously threatened to block main railroads and junctions in August if the government does not halt the project.

Serbia, a candidate for EU membership, is one of Europe's most polluted countries and will need billions of euros to meet the bloc's environmental standards if it wants to join.