US President Donald Trump on Wednesday promised $5,000 to every American adult if Republicans retain control of Congress in November, coupling the extraordinary claim with a plea for his supporters to "pretend" he was on the ballot. "If the Republicans win, you win with us and you get $5,000. It will be called the Trump dividend," he told the Republican midterm convention in Dallas, as the party struggles in polls against the Democrats. The president did not say where the money would come from – with the theoretical bill likely topping $1 trillion – citing only that "our country is making so much money". Watch moreTrump 'believes in the power of his own charisma', analyst says Doubling down on his bet that he can help Republicans defy opinion polls and retain both houses of Congress on November 3, Trump said: "I'm asking you to pretend that I'm on the ballot." "I'm on the ballot, I'm on the ballot – just one more time," he told the crowd. Opinion polls overwhelmingly show that Trump's approval ratings are in the low 30s, as voters become increasingly angry about high prices and the war he launched against Iran. Decision Desk HQ projects Democrats to win the House 230-205 and the Senate to finish 51-49 in their favour in November. Trump defends Iran war Trump strongly defended the unpopular Iran war, predicting victory and linking it directly to lower oil prices – before suggesting the strategically vital Strait of Hormuz should be renamed after him. "Food prices and almost every other item are rapidly going down. And by the way oil will be going down as soon as we win the war with Iran, which is taking place right now," Trump said. Trump also echoed other Republicans at the convention stirring up what he claimed was a wave of "communism" threatening the United States. Read moreTrump casts Democrats as red 'menace' with McCarthyist rhetoric ahead of US midterms "It's going to be a communist country if they win," he said. "Your vote will decide whether our country stumbles at the starting gate of the next 250 years or surges forward and never ever looks back," he said.