UNITED NATIONS, United States — UN Secretary General Antonio Guterres on Tuesday will deliver his first address to the Security Council since taking office, making the case for a new, more assertive diplomacy backed by world powers.

Guterres took over from Ban Ki-moon on January 1 with a pledge to shake up the world body and boost efforts to tackle global crises - from the carnage in Syria to the bloodshed in South Sudan.

The former prime minister of Portugal and UN refugee chief faces a deeply divided Security Council which has been unable to take decisive action to end the war in Syria, now in its sixth year.

"The greatest shortcoming of the international community today is its failure to prevent conflict and maintain global security," Guterres wrote in an op-ed published in the US magazine Newsweek on Monday.

"Where wars are already raging, we need mediation, arbitration and creative diplomacy backed by all countries with influence," he added.

The UN chief’s first formal appearance at the council will be during a debate on conflict prevention led by Swedish Foreign Minister Margot Wallstrom, whose country holds the council presidency this month.

At least nine of the 15 council members will be represented at the ministerial level to hear Guterres lay out his action plan as the world’s diplomat-in-chief.

Among the expected changes is a more hands-on approach from the new secretary general, in what is seen as a shift from Ban who left most of the mediation to his special envoys.

Trouble from Trump? 

Complicating Guterres’ plan to revitalise UN diplomacy however is the question mark hanging over the foreign policy of the new US administration under President-elect Donald Trump.

Guterres spoke with Trump by phone last week and the conversation was described by a UN spokesman as "very positive" after the president-elect dismissed the world body as "just a club for people to get together and have a good time".

After the council voted to demand an end to Israeli settlements in Palestinian territories, Trump warned "as to the UN, things will be different after January 20th" when he takes over at the White House.

In his first days in office, Guterres has stressed the need to reform the United Nations, a message that could win over the new leadership in Washington.

In particular, he has ordered a review of the UN response to sexual abuse by peacekeepers - a move that will likely please US Republicans who complain loudly about US funding of UN missions.

Guterres next week makes his first venture overseas as UN chief, heading to Geneva to shore up Cyprus peace talks and to meet Chinese President Xi Jinping, whose support for the United Nations has been steadily growing. — AFP