Rio Tinto on Tuesday pushed back its timeline by a year to 2027 for first saleable production at its $2.4 billion Serbia lithium project, saying it faces delays in key approvals and protests over environmental concerns.

The mine has faced opposition from environmental activists and local communities over concerns of environmental damage, forcing the local municipality last year to scrap a plan to allocate land for the facility.

The Balkan nation will decide whether Rio can proceed with developing the mine after a general election in April, its prime minister told Reuters earlier this month.

"We fully understand the concerns amongst some Serbian stakeholders about environmental impacts and we will continue to engage to demonstrate the project has developed mitigation solutions in the project plan," Rio said in a statement.