US Secretary of State Antony Blinken said Monday he was hopeful Hamas would accept an "extraordinarily generous" offer to halt Israel's Gaza offensive in return for the release of hostages.

"Hamas has before it a proposal that is extraordinarily, extraordinarily generous on the part of Israel," Blinken said in Riyadh at the World Economic Forum.

"In this moment, the only thing standing between the people of Gaza and a ceasefire is Hamas," he said.

"They have to decide -- and they have to decide quickly," Blinken said. "I'm hopeful that they will make the right decision."

"We can have a fundamental change in the dynamic" in more than half-a-year of bloodshed, Blinken said.

A delegation from Hamas was due on Monday in Egypt, which with Qatar has been seeking to broker a deal that would halt the Israeli offensive and see hostages freed.

Blinken also discussed the ceasefire proposal on Monday in Riyadh with Foreign Minister Hakan Fidan of Turkey, where Hamas maintains an office and the Hamas chief Ismail Haniyeh is a frequent visitor.

Blinken in the talks with Fidan "urged that all efforts be brought to bear to convince Hamas to accept the immediate ceasefire proposal that is on the table," a State Department statement said.

Turkey recognises Israel but President Recep Tayyip Erdogan has been a strident critic of its Gaza offensive.

Erdogan has voiced an eagerness for a greater role in mediating the Gaza conflict after Qatar in recent weeks indicated it would take a step back.