An expanded “safe zone” in northern Syria could include as many as 3 million people and stretch for 50 miles as far as Raqqa, the Turkish president, Recep Tayyip Erdoğan, proposed at the UN general assembly as he pressed his case to speed up the resettlement of Syrian refugees living in Turkey.

His idea, viewed as controversial with Kurds in northern Syria and seen by them as a Turkish landgrab, was his main proposal in a speech projecting Erdoğan as a spokesman for Muslims across the world.

He told the UN: “If this safe zone can be declared, we can resettle confidently somewhere between 1 to 2 million refugees. Whether with the US or the coalition forces, Russia and Iran, we can walk shoulder to shoulder, hand in hand so refugees can resettle, saving them from tent camps and container camps.”

He said he was hoping to establish a corridor with an initial depth of 30km (18 miles) and a length of 480km, enabling the settlement of up to 2 million Syrians, adding that “if we can extend the depth of this safe zone to a Raqqa and Deir ez-Zor line, we can increase the number of Syrians who will return from Turkey, Europe and other parts of the world”.

He said such an expanded zone could contain as many as 3 million people, claiming that as many as 500,000 Syrians had been born in Turkey in the last seven years.

Erdoğan said the plan required an international UN-led donor conference with countries currently housing Syrian refugees, especially Jordan and Lebanon, providing financial help for those returning to safe areas.

Kurds in northern Syria fear Turks and their proxy forces will repeat the violent displacement that saw many dislodged from the formerly Kurdish-controlled town of Afrin last year.

Syrian Kurds have conceded to joint US and Turkish ground and aerial patrols between the towns of Tal Abyad and Ras al-Ain, but reject plans for it to be extended any wider.

American support to the Syrian Kurds has been a point of tension between Ankara and Washington since the US military began arming the Kurdish-led Syrian Defence Forces (SDF) in 2014.

The military arm of the SDF is led by the People’s Protection Units (YPG), a Kurdish militia which Ankara views as an extension of the Kurdistan Workers’ party ( PKK). Turkey and the US have designated the PKK, which has waged a three-decade insurgency in Turkey, a terrorist group.

Turkey has joined US-led operations in Syria with two Turkish F-16 warplanes flying over YPG-held Syria.

The Kurds also fear many of the Syrians that might be placed in the safe zone are not native to north-east Syria, and might displace the Kurdish culture and rights.

In the run-up to the general assembly, Erdoğan has been increasingly impatient about the speed with which the US is allowing the safe zone to be established, and pressed Donald Trump to speed up the process. But Erdoğan, in his speech, repeated none of his threats about pushing into Syria unilaterally if his plan is rebuffed by the US.

The Kurds are unhappy after being excluded from a Syrian constitutional committee set up by Russia, with the agreement of the Syrian president, Bashar al-Assad, and designated with preparing a new constitution for the country.

Assad and Russia have stalled on the committee’s composition for more than a year in a bid to strengthen their military position on the ground, and so reduce the claims of the Syrian opposition to seats on the committee.