A soldier based in Hawaii is scheduled to be sentenced on Tuesday for trying to help the Islamic State group.

Sgt. 1st Class Ikaika Kang pleaded guilty in August to four counts of attempting to provide material support to a foreign terrorist organisation. He said he provided classified military documents, a drone and other help.

He agreed when assistant US attorney Ken Sorenson described other support he provided to undercover agents Kang believed were part of the Islamic State group.

By at least early 2016, Kang became sympathetic to the group, Sorenson said. The FBI gathered information from sources he knew, worked with or lived with when it began an investigation in August 2016, Sorenson said.

Kang provided voluminous, digital documents that included sensitive information, including the US military's weapons file, details about a sensitive mobile airspace management system, various military manuals and documents containing personal information about US service members, Sorenson said.

In this undated file image taken from FBI video Ikaika Kang holds an Islamic State group flag after allegedly pledging allegiance to the group at a house in Honolulu. FBI/US Attorney's Office, District of Hawaii via AP

Trained as an air traffic controller with a secret security clearance, Kang also provided documents, including call signs, mission procedures and radio frequencies, Sorenson said.

At one of the meetings with agents, Kang believed were part of the Islamic State, he swore loyalty to the group in Arabic and English and kissed an Islamic State flag given to him by a purported Islamic State sheikh, Sorenson said.

He then said he wanted to get his rifle and fight — 'just go to downtown Honolulu and Waikiki strip and start shooting', prosecutors said in a news release in August.

After that, FBI agents arrested him.

In exchange for Kang's guilty plea, prosecutors said they won't charge him with additional crimes, including violations of the espionage act, other terrorism-related laws and federal firearms statutes. He's expected to receive a 25-year sentence as part of the plea agreement.