US President Donald Trump warned Iran on Tuesday that it must act “fast" as the United States intensifies financial pressure on Tehran, saying there could eventually be no opportunity for the Islamic Republic to “survive as a nation."

Speaking during a meeting with Persian Gulf Arab and other regional leaders on the sidelines of the United Nations General Assembly, Trump said the US is seeking to force Iran to change course.

“We’re completely isolating Iran financially and we’re just putting the pressure on because hopefully they’ll do the right thing fast before it’s too late," Trump said.

“There’s going to be a time when it’s too late and we won’t have a chance of letting them survive as a nation. I would like to see that," he added.

Trump also issued a warning over any renewed activity at Pickaxe Mountain, the heavily fortified facility located near Iran's Natanz nuclear site. The International Atomic Energy Agency (IAEA) recently confirmed that it detected construction activity at the site.

“We may have to blow up another one. Pickaxe Mountain... if we do [see activity], we’ll blow it up immediately," he said.

Earlier Tuesday, Trump addressed the UN General Assembly, where he cited Iran as a major threat and reiterated his opposition to Tehran obtaining a nuclear weapon.

"There is no better example of a danger that was allowed to gather strength at the world’s peril than the number one sponsor of terror, the Islamic Republic of Iran. From the first day I entered the political arena, I have been unwavering - I will NEVER allow Iran to have a nuclear weapon."

Trump said he had offered Iran full economic cooperation after taking office in return for abandoning its nuclear program and support for terrorism, but claimed Tehran rejected the proposal. He also warned that Iran had developed a missile capable of reaching Europe.

"Iran has created a missile that will allow them to strike Europe," Trump warned.

He added, "Their goal was to complete their mad race for nuclear arms behind the defense of ballistic missiles."

Trump said he faces a major decision over how to proceed with Iran and expressed hope that Tehran will agree to a deal following the US midterm elections. "I have a big decision to make. Will a deal be made with Iran that lets them rebuild and create a far greater country than it ever was before, maybe one of the greatest in the Middle East or even the world? Or do I annihilate the Islamic Republic and do it quickly, never giving them a chance to kill and destroy people and countries again? Do I drive them into hell with no chance of survival and no hope of future greatness for generations? But I believe we’ll make a deal right after the election, because it doesn’t make sense for them not to. They’re waiting to see how I do in the midterm election. What they don’t realize is that I’m not running. I did that already and won in a landslide."