European Commission officials will visit the border between Spain and Gibraltar next week to assess the legality of checks on traffic that caused a diplomatic row with Britain.
The delegation will assess border controls and the free movement of people and goods.
Spain imposed strict checks on traffic at the border with Gibraltar in protest at the creation of an artificial reef. They said the 74 concrete blocks on the seabed disrupt an area used by its fishing boats, while the Gibraltarians say it was a necessary environmental measure.
There have been reports of increasing violence at the border since the end of August as angry commuters face long queues to get to homes in Andalusia.
As well as reports of missiles being thrown at Guardia Civil officers, two unions organised a protest after reports an officer was injured by a Gibraltar-registered car that failed to stop.
The protest prompted calls for renewed efforts, involving the European Union, to solve the diplomatic dispute which has seen Madrid introduce additional checks at the border in protest at what it sees as an encroachment on its fishing rights, leaving workers and tourists facing hours in queues to get through.
In a statement, a Commission spokesman confirmed the date of the visit. He said: "President Barroso spoke today with prime minister Rajoy.
"They decided that the mission - as was agreed on August 19 - will visit the border between Spain and Gibraltar, on 25 September to assess border controls and the free movement of people and goods, including fraud and smuggling.
"It was also agreed that the complaints made by Spain regarding the dumping of concrete blocks and the re-sanding in the context of the Eastside project will be dealt with in parallel and with the necessary thoroughness by the European Commission."