U.S. Secretary of State John Kerry on Thursday urged Syria's embattled President Bashar al- Assad to end the killing in the Arab country.

Citing a phone conversation with Saudi Arabia's foreign minister, Kerry said at the State Department that according to the estimate by the Saudis, "perhaps as many as 90,000 people who have been killed in Syria." This number is much higher than the UN estimate of a death toll of nearly 70,000.

The "vast numbers of refugees" creates enormous dislocation and burdens on the countries that are prepared to receive them, he said in a press conference before meeting with UN Secretary- General Ban Ki-moon, adding that Syria will top the agenda in his discussion with Ban.

"President Assad has the ability to be able to make the difference here by deciding to engage in a legitimate diplomatic process," Kerry told reporters. "He must end this killing."

Kerry noted that he will talk with the UN chief on how to " change President Assad's calculations, to stop the bloodshed and begin a peaceful political transition" in Syria.

He also called on the international community to respond to the UN's appeal for more funds and more humanitarian assistance to help the violence-affected Syrians both inside and outside the country.

The UN estimates that more than 750,000 people have fled Syria to seek refuge, while about 2.5 million people are displaced within the country.