ReutersHILLA, Iraq: The local official drew a line on a map slicing through farmland and desert southwest of Baghdad whose Sunni residents have been displaced by fighting, and then pointed just south to the site of the most revered Shiite shrine.

The line marks the course of a 45-kilometer trench designed to safeguard the Shiite holy city of Karbala from ISIS militants who seek its annihilation, said Babel provincial councilman Hasan Fadaam.

“As long as ISIS is in Anbar, this trench will be used to protect the residents of both Babel and Karbala, which will become a launching point to liberate [Anbar],” he said.

However, many Sunnis fear that the trench is not a temporary security measure but just one more example of how they are being expelled from sensitive areas in central Iraq, which they say the Shiite majority wants to control.

The trench and an accompanying berm, now more than half built, wind through traditional Sunni tribal lands whose civilian population has been caught in the crosshairs between ISIS insurgents and military offensives by Shiite militias and Iraqi security forces.

“The goal is for the Shiite militias to cleanse the Sunnis from the area,” said a sheikh from Al-Aweisat, an agricultural region about 40 km southwest of Baghdad that has been cut up by the trench. “This is a separation line between the Sunnis and the Shiites,” he told Reuters.

During the last year of war, tens of thousands of people, most of them Sunnis, fled this stretch of farmland straddling western Anbar province, which ISIS militants control and use to cross into their Syrian strongholds, and Shiite areas to the east and south in Babel and Karbala provinces.

Fadaam told Reuters traffic would be funneled through guarded entry points. Watch towers will be constructed every 500 meters along with security cameras and barbed wire, he said, although budget constraints have delayed those installations.

An earlier proposal to build a concrete wall was dismissed as unnecessary and symbolically problematic.

“Topographical change is happening. This has become clear,” said Atella Mahdi al-Hemos, a moderate Shiite sheikh from Babel, predicting that the trench would lead Iraq toward partition.

“You won’t enter without a badge. The badge ends up becoming a passport.”

The ISIS-led advance of insurgents last year increased speculation about the splintering of Iraq into Shiite, Sunni Arab and Kurdish regions, but irregular fault lines between the groups would require mass population transfers for that to happen.

Shiite officials and tribal leaders deny that the trench – 3 to 5-meters deep and 3 to 4-meters wide, will bring about such a reconfiguration.

“It has no sectarian dimension. It only has a security dimension: to protect the people, Sunni and Shiite alike, from the destruction of ISIS,” said Sadoun Muhsin al-Kilabi, a sheikh from Mahmudiyah, 20 km east of the trench.

He told Reuters that security forces lacked the numbers to secure all areas, making “defensive lines” like the trench a tactical necessity.

Iraq’s army nearly collapsed last summer despite receiving billions of dollars in support during the U.S. occupation that ended in 2011. It is now complemented on the battlefield by a mix of Shiite militias and volunteer fighters.

Proponents say the barrier is required to secure military gains and population centers in the south, a stronghold for the Shiite majority that has dominated the country since the U.S.-led invasion in 2003 toppled Saddam Hussein, a Sunni.

“After the liberation of Anbar, the barrier will be removed completely,” said Fadaam, the local official.

ISIS moved into Anbar’s two main cities of Fallujah and Ramadi a year ago, then expanded control of large swaths of the province during last summer’s dash across the Syrian border.

Some of those gains have been rolled back, but political divisions have undermined further efforts, and the eradication of the ultra-radical Islamist group from Anbar’s vast desert territory could realistically take years.

In the meantime, the trench may help determine how central Iraq is repopulated, with physical partition becoming a reasonable option.

Shakir al-Essawi, city council chairman of Amiriyat al-Fallujah, 20 km west of the trench, said local protests have managed to freeze the digging for now.

But he fears what could happen if the trench is completed.

“Maybe in the future they will offer land in another place and ask people to move there and they can build houses,” he said.

“They will forget about [this] area and it will become part of Shiite Babel.”