U.S. Secretary of State Rex Tillerson has asked Iraqi Kurdistan’s President Masoud Barzani to postpone holding the region’s independence referendum, which is expected in September, Rudaw reported.

In a telephone conversation on Thursday, Tillerson and Barzani discussed the upcoming referendum, bilateral relations and the war against ISIS.

A statement from the Kurdish Presidency said Barzani is not convinced there is an “alternative” to the referendum at this stage.

“The US Secretary of State...also stated he would rather see the referendum in Kurdistan to be postponed, and he reiterated his support for dialogue and negotiation between the [Kurdistan] Region and Baghdad,” the statement read.

“On the issue of postponing the referendum President Barzani said to the US Secretary of State that the kind of coexistence that the Kurdistan Region had worked for with the state of Iraq in the past and over various stages was not implemented, and that is why the people of Kurdistan have decided to take their own path,” it added.

Back in June, Barzani announced on Twitter that the northern territory would hold an independence referendum on September 25.

Following the announcement, the Iraqi government issued a statement in response that it would reject any unilateral move by the Kurdish regional authorities to push for independence.

Haidar al-Abadi, Iraq’s prime minister, said on June 13 that the decision was untimely.