Turkish President Erdogan says Turkey, US, should back Free Syrian army, clear ISIS capital.

Turkish President Recep Tayyip Erdogan on Saturday called on the United States to militarily help his country fight ISIS.

With US help, Turkey could launch a major offensive, Erdogan said, with the goal being to attack ISIS' capital of Raqqa, Syria.

"The huge America, the coalition and Turkey can join hands and turn Raqqa in to an ISIS graveyard," Erdogan said at an Istanbul press conference. "They will look for a place for themselves to hide."

"We now need to clear Manbij from them. Once we clear Manbij, the real center is where? In Raqqa. It is thought that an estimated 2,500 to 5,000 Daesh (ISIS) terrorists are in Raqqa. Now Turkey, the Free Syrian Army, along with the coalition led by America, can clear these 2,500 to 5,000 terrorists.

"This is not difficult for us and we would succeed.

"I believe we can succeed and I will tell this to Mr Trump. Come let's do this together and let's clear this area of terror organizations."

Erdogan also called on Washington to cease supporting the Kurdish People’s Protection Units (YPG) as allies in the fight against ISIS, since it damaged "the spirit of solidarity" with Turkey.

The Kurdish forces aided the Syrian Democratic Forces in killing over 40 ISIS members in Raqqa since Thursday.

Erdogan said he would present US President Donald Trump with "documents" proving the Kurdish fighters are in fact linked to the Kurdistan Workers' Party (PKK) and are therefore a "terrorist organization."

"We can never accept their co-operation with a terror organisation, which is threatening our people's lives under the pretext of fighting against Daesh," Erdogan said. "The fact that the US is acting together with YPG and PYD and giving them concrete support is damaging the spirit of alliance and partnership."

"We are telling American friends so as not to take a terror group along with them."

Both Turkey and the US consider the YPG to be a terrorist organization.

Erdogan, who wants a "fresh start" for US-Turkey relations, is scheduled to meet Trump on May 16 in Washington.