UNITED NATIONS -- UN Secretary-General Antonio Guterres on Wednesday called for strong collective action to deal with the serious challenges to UN peacekeeping.

UN peacekeeping faces serious challenges, particularly in four of its largest deployments: Mali, the Democratic Republic of Congo, the Central African Republic, and South Sudan, Guterres told the Security Council in a high-level debate on peacekeeping.

"UN peacekeeping missions now operate in far more dangerous, complex and high-risk environments. They are under threat from armed groups, criminals and terrorists, who have access to powerful modern weapons," he said. "UN peacekeepers are often under-equipped, under-prepared and unready for the dangerous environments in which they now operate. There are gaps in command and control, in culture, in equipment and in training."

UN peacekeepers are vulnerable and are targeted for attack, said Guterres. Last year, 59 UN peacekeepers were killed in malicious acts, a sharp increase from 2016, when the figure was 34.

"We are damaging the instrument of peacekeeping, and indeed multilateralism itself, in creating unrealistic expectations. Lives and credibility are being lost," he said. "These challenges require strong, collective action."

He asked to refocus peacekeeping with realistic expectations; to make peacekeeping missions stronger and safer; and to mobilize greater support for political solutions and for well-structured, well-equipped, well-trained forces.

The United Nations is working to improve the safety and security of peacekeepers, he said. "We have already started to implement measures to improve the preparedness and response of missions at high risk by strengthening training, reviewing medical support, and addressing performance issues."

The world body is conducting independent reviews of the peacekeeping missions in a bid to refine their priorities and configuration, while assessing the viability of mandates and political processes. The goal is to ensure that the peacekeepers are well-trained, well-equipped and better postured for challenges and threats. "Too often in the past, our troops have been reduced to waiting in a defensive posture, giving hostile forces time and space to plan attacks," he said.

Guterres said he has launched a new approach to sexual exploitation and abuse by peacekeepers so that victims have a clear way to report allegations, and the United Nations can work with troop- and police-contributing countries to address the allegations, end impunity and prevent future cases.

He stressed that efforts on the side of the United Nations, although critical, are not enough to meet the challenges. "Our chances of success increase dramatically when we work together with member states and share burdens, risks and responsibilities. We urgently need a quantum leap in collective engagement."

Guterres said he is launching a new initiative called Action for Peacekeeping in a bid to mobilize all partners and stakeholders to support UN peacekeeping.

He asked the Security Council to sharpen and streamline mandates for peacekeeping missions. "Please put an end to mandates that look like Christmas trees."

"By attempting too much, we dilute our efforts and weaken our impact," said the UN chief.