Iran war won't end until after crucial November elections, says Trump

US President Donald Trump has said he does not think the Iran war will end until after November's midterm elections, adding that oil prices will not come down until then.

"I think the war's going to end immediately after the election because they can't hold out any longer," Trump said of Tehran on Wednesday.

He made the comments as he headed to Texas for the party's first-ever midterm election convention - and repeated it there, arguing that short-term economic pain was worth it to prevent Tehran from developing nuclear weapons.

Trump is facing falling polling numbers and pressure from within his Republican Party to end the war with Iran.

"Right after the election, oil prices are going to be tumbling downward," Trump told reporters. "I think it's going to take a little bit longer than the midterm."

He added that Iran was "desperate to try and affect the election, so that we can get a nice weak group of people in there" - an apparent reference to the Democrats - "and leave them alone and let them have their nuclear weapon".

He provided no proof of the election claim. Tehran has repeatedly denied it is seeking nuclear weapons.

At the convention in Texas, Trump echoed some of these lines, saying the price of oil would tumble "as soon as we win the war with Iran".