A US pastor has spent $4,000 of his own money buying weapons for a Christian militia engaging ISIS forces in Iraq.

William Devlin is a pastor at Infinity Bible Church in the Bronx, New York City. He has supplied the Nineveh Plain Protection Units (NPU) with a selection of AK-47 assault rifles, grenades, and rocket-propelled grenade launchers.

The NPU consists mainly of Assyrian Christians attempting to defend their region from ISIS. However, it frequently finds itself outmatched and outgunned.

Speaking to the Christian Post last week, Devlin said he had gone to speak to NPU leader General Behnam Aboosh to offer his support, but the general had responded that what was needed was quality weapons.

He told Devlin: 'Look, I am dealing with a major military force that has United States weapons that they got from the Iraqi Army. ISIS has all these heavy weapons, all these armoured vehicles, and I am sitting here in the Nineveh Protection Unit with the equivalent of bows and arrows.'"

Devlin said he then offered to buy weapons for the NPU.

The next day, weapons were delivered from an Assyrian arms dealer. The militia has previously received training from US military personnel, but Devlin says they have not received any actual weapons. He said: "I was not going to go away from the general without helping him in some practical, demonstrable way."

Last week, Devlin posted pictures to Facebook of the weapons he acquired. He wrote in his post: "[I'm] grateful that, with personal money, I can purchase items that can assist and protect the Christians and their cities in the Nineveh Plain of Iraq from ISIS."

Devlin said that the US State Department is aware of his dealings: "They know the type of stuff I do. As far as I know, other than the big organizations, I don't know of any other American Christian pastor that is going in the refugee camps to help the Yazidi people and help the Christian people there. I don't know of anybody else that is going in."

It was reported last week that the NPU won a victory against ISIS forces when they liberated the Iraqi town of Badanah, assisted by airstrikes from a US-led international coalition.

After its initial dramatic successes in Iraq and Syria, ISIS has come under increasing pressure in both countries and is losing territory to both government and rebel forces. In what may prove to be a decisive move, Turkey has signalled its willingness to join the US in attacking the ISIS stronghold of Raqqa in Syria.