The US-backed Syrian Democratic Forces have begun an offensive to capture the northern city.
Johannes de Jong works closely with Syriac-Assyrian Christians involved in the campaign. He gave Premier News Hour a description of the resistance Christian fighters face from ISIS.
He said:"The very clear picture they're giving me is that there's a wall around Raqqa, they put it full of mines.
"You have to imagine a situation where they have to fight for every street and every house.
"It will be bad. There are still a lot of civilians they [ISIS] will use as human shields.
"They still have high end military equipment they stole in their past from places like Mosul. It will be tough".
De Jong said the Syriac-Assyrian Christians are desperate for the support and prayers of the international Christian community.
He said prayers should be focused on strength and resources for the fighters.
"Pray that as many as possible will make it through and this fight will not be too long.
De Jong added: "Pray that there will be guns and ammunition for Syriac-Assyrian Christians while part of this fight to liberate Raqqa.
"Your prayer shouldn't be lofty, but we should pray to Jesus for the daily bread."
