US has become 'third world country': Trump

Republican presidential front-runner Donald Trump has said the US has now become a "third world country" as compared to infrastructures in Dubai and China, and promised that things would change once he is elected the American president.

"We have become a third world country, folks!," Trump, 69, told his supporters at an election rally at Sal Lake City in Utah, which goes to presidential primary elections on Tuesday.

"If you go to places like Dubai, China, you look at the roads, at the rail roads, they have the bullet trains that go 100s of miles an hour. And if you go to New York, they're like 100 years ago," he said.

Trump said that the US under him would knock out the ISIS and rebuild the country.

"When it comes to trade, we are going to start being smart, because our country is poor. We are going to make American so great again. It is not great now. We need education to that," he said.

Reiterating that Trans Pacific Partnership is a "disastrous" trade deal, Trump said the US under him would have deal that would favor America.

"It is not a question of free trading. Free trading is wonderful. The problem of free trading is that we need smart people on our side also. If I am the president, I guarantee you they (Mexico) would pay (for the wall) and they would be very very happy about it," he said.

Trump said his administration would negotiate great trade deal amid applause and cheer from the audience.

"We are going to bring wealth back again because our country is a poor country. We have a deficit that you can not believe. We're sitting on a bubble, very dangerous bubble. We are sitting on a big fat ugly bubble. At some point unless we act quickly and smartly, it is going to explode. You need the right people. We have the wrong people now," Trump said.

He promised his supporters that things would start changing fast if he is elected the president.

Trump's address in Salt Lake City was the first election rally after his impressive victories in three states of Florida, Illinois and North Carolina on Tuesday.

On March 22, the presidential primary is scheduled to be held in American Samoa, Utah and Arizona which have more than 100 delegates in all.

Trump currently is leading the delegate count with 678. He is followed by Texas Senator Ted Cruz (423) and Ohio governor John Kasich (143). To become the Republican nominee for the November 8 presidential elections, Trump needs 1,237 delegates.