Jeremy Corbyn, 68, said he was “very concerned” about how soon the US president was invited by Prime Minister Theresa May – just a week after he took office in January.
In an interview with the Independent, Mr Corbyn said: “Obviously there have to be relations with the USA.
“My views on Donald Trump’s statements and utterances during the Presidential election are extremely well known.
Labour leader Jeremy Corbyn has hinted he could postpone Donald Trump's state visit
"There has to be a relationship with the US Government, you have to tell them what you believe.”
Mr Trump was initially due to cross the Atlantic in June but the visit was postponed until early October.
Mr Corbyn also pointed out that the former US President Barack Obama had to wait three years into his administration for his first state visit.
The TV election debate – in pictures Wed, May 31, 2017
The televised debate saw Jeremy Corbyn, Amber Rudd, Paul Nuttall, Caroline Lucas, Angus Robertson, Tim Farron and Leanne Wood go toe-to-toe
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The politicians taking part in the debate
My views on Donald Trump’s statements and utterances during the Presidential election are extremely well known
Labour leader Jeremy Corbyn
When Mr Obama did visit in 2011 he met David Cameron, then the Prime Minister, at Downing Street and was greeted by the Queen as well as senior members of the royal family at Buckingham Palace and delivering a speech in Westminster Hall.
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Mr Corbyn added: “George Bush, second term. Reagan, second term. I think they were all second term.”
Asked if the Republican leader should have to wait until a potential second term in office, the Labour leader replied: “Well, it’s not up to me as the invitation has already been issued.”
Donald Trump meets Theresa May in the White House in January 2017
When asked on whether Mr Trump would be welcome here in October – the date believed to have been pencilled in by officials – he added: “Well, let’s find out that on June 9.”
Labour’s Shadow Foreign Secretary Emily Thornberry had previously stated that Mr Trump’s state invitation would not be rescinded but did not comment on a possible date for the trip.
Donald Trump's visit to the UK could be postponed if Jeremy Corbyn becomes PM
When the original trip was announced it was met with widespread protests. A petition gained 1.85 million signatures appealing for Mr Trump’s state visit to be blocked.
Express.co.uk is waiting on a response from the Labour Party.