Saudi Arabia has called for "urgent" United Nations reforms to confront world challenges such as the Palestinian-Israeli conflict, the wars in Syria and Yemen, terrorism and the refugee crisis.

"The type and scale of the challenges we confront require us to work hard toward the reform of the United Nations system, increase the effectiveness of the Security Council, and revitalize the role of the General Assembly and all the relevant bodies of the United Nations," Crown Prince Mohamed bin Nayef bin Abdul Aziz Al Saud said at the General Assembly's annual general debate on Wednesday.

The reforms he proposed included increasing the numbers of the 15-member Council, whose resolutions have binding legal force, and enhancing the powers of the Assembly, whose decisions currently lack this.

He also called for an end to the Israeli occupation of Palestinian and other Arab land, condemning Israel's "terrorist practices and acts of aggression".

"Achieving any progress in ending the Palestinian-Israeli conflict seems impossible in light of the continuation of the Israeli settlement policy, the tampering with the holy city of Jerusalem ruining the Arab, the Islamic and Christian identity of the city, and the heartless policy of repression practiced against the Palestinian people," he said.

On Syria, the Prince called for transition by supporting the moderate opposition, blaming the international community for failing to "to take concerted decisions to save the Syrian people from the crimes that take place there, murders, destruction and displacement all of which is made by President Bashar al-Assad".

He added that his country was keen to help Syrian refugees in neighbouring countries, only one day after he announced that Saudi Arabia would provide an additional $75 million to aid refugees in coordination with international aid organisations.

Saudi Arabia has already provided in excess of $800 million in support to refugees in countries neighbouring Syria, he said on Tuesday.

The Prince also condemned Iran's support for "terrorist militias' groups" in Bahrain, Kuwait, Yemen, Iraq, Syria, Lebanon, and elsewhere, as well as its "dissemination of sectarian speech".

"The Government of the Kingdom of Saudi Arabia calls upon the Islamic Republic of Iran to desist from all of the policies of discrimination, racism and sectarianism and to begin to build positive relations with its neighbours on the basis of the principles of good-neighbourliness and non-interference in the internal affairs of other States," he said.

The type and scale of the challenges we confront require us to work hard toward the reform of the United Nations system, increase the effectiveness of the Security Council, and revitalize the role of the General Assembly and all the relevant bodies of the United Nations.

- Mohamed bin Nayef

Saudi-Iranian relations have been strained since Iran criticised Saudi Arabia's handling of a deadly hajj stampede last year, with more tensions rising after Saudi Arabia executed prominent Shia cleric and activist Sheikh Nimr al-Nimr in January, leading the two countries to eventually break ties.

The Crown Prince also denounced recent United States congressional action to allow Americans to sue Saudis in connection with the terrorist attacks of 11 September 2001, as "a serious threat to the sovereign rights".

Behind the scenes, Riyadh has been lobbying for the Justice Against Sponsors of Terrorism Act to be scrapped.

Meanwhile, White House officials say Obama will reject the bill by the Friday veto deadline.

The administration is worried the bill - passed unanimously by Congress - would undermine state immunity, setting a dangerous legal precedent.

Families of 9/11 victims have campaigned for the law - convinced that the Saudi government had a hand in the attacks that killed almost 3,000 people.

Fifteen of the 19 hijackers were Saudi citizens, but no link to the government has been proven. TheSaudi government denies any links to the plotters.