Trump, meanwhile, acknowledged that oil prices were "temporarily high" but said "our country is getting stronger and stronger all the time, and those pump prices are going to come down".

The Republican president has faced significant pressure to lower fuel prices, which have jumped due to the wars in Iran and Ukraine.

Talking up the economy, Trump told the crowd in Perry "we're taking in massive amounts of money through tariffs" and repeated his pledge to offer every adult American a $5,000 (£3,700) payout if Republicans win both chambers of Congress.

He also took aim at the Democrats, telling the crowd they would "loot your wealth" and "annihilate your borders".

Using derogatory language, he accused the Democrats of trying to open up immigration from Libya, Yemen, Haiti and Somalia - countries which he described as "terror-infested".

Describing a previous meeting with several senators, he recalled: "I said, 'Why do we always have to take people from shithouse countries? Why can't we take people from, like, well... Norway, Sweden? Why not Denmark?'"

Read More