Among his many rebukes of the modern United Nations, President Donald Trump denounced immigration policies.

"Your countries are going to hell," Trump told the U.N. General Assembly in his near hour-long speech Tuesday in New York City, calling "uncontrolled" migration the "No. 1 political issue of our time" and pinning the blame on the weakness of the U.N.

"Your countries are being ruined," Trump warned. "The United Nations is funding an assault on Western countries and their borders."

Trump called on member states to join him in forging "a safer, more prosperous world," warning against nuclear and biological threats while insisting that sovereign nations must retain control of their borders and destinies.

"I'm really good at this stuff," Trump said. "Your countries are going to hell."

Trump accused the U.N. of not only failing to stop migration but of effectively enabling it, telling delegates that "the United Nations is funding an assault on Western countries and their borders."

"Not only is the U.N. not solving the problems it should, often, it's actually creating new problems for us to solve," Trump said.

The "globalists" at the U.N. should fix their homelands first, instead of trying to weigh in on global problems they are never able to solve with their "empty words," Trump said.

"I encourage all countries to take their own stand in defense of their citizens as well," he continued. "You have to do that because I see it – I'm not mentioning names – I see it, and I can call every single one of them out.

"You're destroying your countries. They're being destroyed. Europe is in serious trouble. They've been invaded by a force of illegal aliens like nobody has ever seen before. Illegal aliens are pouring into Europe.

"And nobody's doing anything to change it, to get them out. It's not sustainable. And because they choose to be politically correct, they're doing just absolutely nothing about it."

While he said he did not name names, Trump did talk specifically about London under Mayor Sadiq Khan.

"I look at London, where you have a terrible mayor, terrible, terrible mayor, and it's been so changed, so changed," Trump said. "Now they want to go to Shariah law."

Doing that would radically change the country, Trump warned.

"You're in a different country; you can't do that," he said. "Both the immigration and their suicidal energy ideas will be the death of Western Europe."

Something must be "done immediately," according to Trump, because "this cannot be sustained."

"What makes the world so beautiful is that each country is unique," he said. "But to stay this way, every sovereign nation must have the right to control their own borders. You have the right to control your borders, as we do now, and to limit the sheer numbers of migrants entering their countries

"They put their blood, sweat, tears, money into that country, and now they're being ruined. Proud nations must be allowed to protect their communities and prevent their societies from being overwhelmed by people they have never seen before, with different customs, with different religions, with different everything."