The UN secretary general, António Guterres, warned on Tuesday that if Donald Trump withdraws from the Paris climate agreement, there could be negative economic, security and societal consequences for the US.

Guterres issued the warning after calling on world leaders to adhere to the agreement in his first major speech on climate change as secretary general.

His remarks at New York University came as the world waits for Donald Trump to announce whether the country will continue to uphold the Paris deal, which nearly 200 countries signed as a commitment to reduce greenhouse gas emissions.

In a question-and-answer session after the speech, a student asked how the US can address climate change when its president has threatened to back out of the Paris accord.

“If someone leaves a void, I guarantee someone will fill it,” said Guterres, who went on to explain what consequences such an exit could have for the US. “Today, the economy and social aspects are linked to the environmental aspects, but they are also linked to the security aspects, they are linked to the risks of conflict.”

He continued: “if you leave a void to others to occupy, you might be creating a problem to your own internal security.”

Guterres said that if the US does withdraw from the agreement, it is important that American cities, states and businesses remain engaged with the goals the deal outlined.

Trump’s threat has concerned leaders around the world, but Guterres, who became secretary-general on 1 January, has said the accord is not dependent on the US government’s participation.

The White House press secretary, Sean Spicer, said Tuesday that Trump “wants a fair deal for the American people”, adding that Trump was spending a “great deal of time” considering the agreement.

Trump said on Saturday that he would announce this week whether the US would adhere to the Paris agreement after resisting pressure to announce the plans at the G7 summit. The other G7 countries – Germany, France, Britain, Italy, Canada and Japan – reaffirmed their support for the accord last week.

The landmark agreement was signed in December 2015 and has been ratified by 147 countries, including the US.

To underline the importance of the agreement, and other UN climate goals, Guterres spoke broadly about the threats climate change poses to the world, saying “the world is in a mess” because countries and communities everywhere are facing pressures such as overpopulation, water scarcity and food insecurity.

He warned that “climate change is a multiplier of many other threats” including poverty, displacement and conflict, and that the people hit “first and worst” by climate change are the poor, vulnerable and marginalized.

“It’s absolutely essential that the world implements the Paris agreement and that we fulfill that duty with increased ambition,” he said.

Guterres said addressing climate change was an economic necessity and highlighted the threat climate change posed to national security, noting that more than 24 million people in 118 countries were displaced by natural disasters in 2016, which is three times as many people as were displaced by conflict.

Guterres, the former Portuguese prime minister, also announced that there would be a UN climate summit in 2019.

His comments on the US were consistent with statements he has made since replacing Ban Ki-moon as secretary general this year.

“Even if some national governments backtrack in commitments, the combined impacts of sub-national authorities, businesses and civil society will create an unstoppable momentum,” Guterres said at a climate change meeting at the UN headquarters in New York in March.

Last week, Guterres told the BBC the agreement would “not collapse” if the US backed out. “I think it is very important that the American government stays engaged, but this is not the end of the world,” he said.

Guterres did not specifically mention Donald Trump in the speech, but said his “door is open to all who wish to discuss the way forward, even those who might hold divergent perspectives”.

He said each month, countries were moving to translate the Paris agreement into national plans.

“Yes, not everyone will move at the same pace or with equal vigor,” Guterres said. “But if any government doubts the global will and need for this accord, that is reason for all others to unite even stronger and stay the course.”