Protesting farmers have been told not to bring their tractors to Cardiff.
South Wales Police said it was aware of a protest planned to take place in Cardiff Bay on Wednesday.
A spokesperson for the force said it was scheduled to begin at 12.30pm and expected to attract large numbers.
Officers say they are “monitoring this situation closely” as road users are told they could experience delays.
The protest may include slow-moving traffic in the Cardiff Bay area and in the wider South Wales area, police say.
But the force says it will be “proactive in minimising disruption to the public”.
There are currently no planned road closures, but access to some roads around the Senedd will be controlled.
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Farmers have expressed their unhappiness at new plans from the Welsh government which would see changes to how farms receive government funding.
A new scheme is being introduced in Wales after the UK voted to leave the European Union.
The Welsh government’s proposals would see farms getting public money if they meet a series of environmental targets.
This includes making sure that 10% of farmers’ land is covered with trees.
Farming unions have warned about the impact the requirement could have on the future of the industry.
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The Welsh government has emphasised the proposals are subject to an ongoing consultation.
Superintendent Esyr Jones said the force “respects the right to peaceful protest”.
“We are in discussions with the organisers to ensure that the protest takes place safely, lawfully with minimum disruption to the wider public,” he added.
“While there is an agreement to facilitate protest activity outside the Senedd, I would urge protesters not to bring tractors or other agricultural vehicles to the protest.
“There are concerns that they pose a risk to the safety of other road users and restrict the movement of emergency services in a busy city environment.”
The public have been advised by police to plan their journey accordingly amid expected delays.