Police tried to negotiate with protesters including MP Caroline Lucas for two hours before arresting her, a court was told.
Superintendent Jane Derrick told Brighton Magistrates’ Court that she was trying to ensure the safety of protestors and Cuadrilla staff at exploratory oil drilling site in Balcombe, on August 19 last year.
The court was told officers on the ground were trying to get the demonstrators to move from the only emergency access to the site.
She said a number of people were locked together at the entrance of the site and police liaison officers were sent in to ask them move.
Ms Derrick said: "We used a tiered response, asking people to unlock themselves, get up and to walk away from the entrance.
"We were not containing people, we were allowing them to walk away from that area."
She told the court her officers spent more than two hours trying to negotiate with the protesters sat in front of the entrance but that the information coming back to her was that the protesters wanted to remain in front of the entrance all day.
Ms Derrick said although no drilling was taking place that day there were still staff on site, and deliveries of equipment, water and food supplies were made on Monday, Tuesday, Thursday and Friday, expected that day.
She also said due to the nature of the equipment being used at the Cuadrilla site, there needed to be emergency access maintained at all times.
Supt Derrick said she also believed the protesters at the climate camp had the means and equipment to cause disruption.
Ms Derrick said: "It was clear to me I should do everything I could do to facilitate a peaceful protest but the main concern was safety.
"I made it very clear to them that I was willing to negotiate and that being there all day was not acceptable and that if they continued not to comply then the likelihood was that they would be arrested."
Lucas, from Brighton; Josef Dobraszczyk, 22, from Bristol; Ruth Jarman, 50, from Hook, Hampshire; Sheila Menon, 42, from north east London; and Ruth Potts, 39, from Totnes, Devon, all deny wilful obstruction of the highway and breaching Section 14 of the Public Order Act.
The trial continues.