The US-backed Syriac Military Council (MFS) is calling on the United States to defend thousands of Christians in northeast Syria against a potential attack from Turkey.

On Wednesday, the council sent out a plea to Christians in the US.

"The Turkish army started to remove the wall between Turkey and Northern Syria in the Tal-Abyad area. Turkey has amassed its forces and its jihadist proxies at that point. It clearly aims to invade Northern Syria," the council wrote in a press release.

"Turkey aims to kill and destroy us and to finish the genocide against our people. {There} are still more than 100,000 Syriac Christians living in NE - Syria and they will be killed or driven away if Turkey invades."

The Syriacs are one of the oldest Christian communities in the world. Many of them died in the fight against ISIS.

The council warns that churches will be burned and Christians will be killed if there is an attack from Turkey.

"We hope and pray that as we have defended the world against ISIS, the world will not abandon us now. Now is the time for Christian, Western countries, and for Christian churches and believers worldwide, to protect our Christian people in NE Syria from falling victim to brutal war, dictatorship, fascism, and radicalism."

The US sent a strong warning to Turkey on Wednesday after learning of the Turkish military's actions on the northern Syrian border.

US officials believe Turkey is planning to retaliate against US allies in the region after the US sanctioned Turkey for buying S-400 missile defense systems from Russia.

"Unilateral action into northeastern Syria by any party, particularly as U.S. personnel may be present or in the vicinity, is of grave concern. We would find any such actions unacceptable," Pentagon spokesman Navy Cmdr. Sean Robertson said in a statement.

The US booted Turkey from its F-35 fighter jet program after Turkey bought weapons from Russia last week.

"The F-35 cannot coexist with a Russian intelligence collection platform that will be used to learn about its advanced capabilities," White House spokeswoman Stephanie Grisham said Wednesday.

Turkey is a critical NATO ally but its relationship with the US has deteriorated over time due to what the US believes is President Recep Tayyip Erdogan's increasingly authoritarian leadership.

For the Christian communities on the northern border, this weakening relationship could mean death.

"We urge the Christians in the US to ask that the US Army that is present in North-East Syria will not allow the Turkish army and jihadists to invade North-East Syria," the council said. "Will the US Army stand by idly while we are killed?"