The US president clarified his remarks during an interview with Good Morning Britain's Piers Morgan, held in the historic Churchill War Rooms on the second day of the UK state visit.
He said: "I don't see it being on the table, somebody asked me a question today and I say 'everything's up for negotiation' because everything is, but that's something that I would not consider part of trade."
He said: "I don't know Jeremy Corbyn, I've never met him, never spoke to him, but he wanted to meet today or tomorrow and I decided that I would not do that.
"I think that he is, from where I come from, somewhat of a negative force."
Speaking outside the Foreign and Commonwealth Office alongside the PM, Mr Trump also took aim at Sadiq Khan, saying "he's done a poor job" as London mayor, before heading for a tour of the Churchill War Rooms.
The president was shown around the nerve centre of Churchill’s war effort before meeting Mr Morgan in front of the generator that helped power the fight back against the Nazis in World War II.
In the interview he appeared to back-peddle on his earlier Corbyn criticism, saying he "certainly would" meet the Labour leader in the future.
He said: "I don't know him, he wanted to meet, it was very tough to meet and probably innapropriate to meet to be honest with you.
"A lot of things are happening right now with respect to our country and your country, my country and let's call them almost the same because I feel that way, it's really a tremendous relationship."
He also said Prince Harry "couldn't have been nicer" when the pair met on Monday and denied calling Meghan Markle 'nasty' - as reports had previously suggested.
In a recent interview with the Sun newspaper, Mr Trump said he was unaware that Meghan had previously suggested she would leave the US if he won the 2016 presidential election, adding: "I didn’t know that she was nasty."
The US leader clarified those comments, saying he had not known that Meghan had been nasty about him.
He said: "They said some of the things that she said and It’s actually on tape.
"And I said: ‘Well, I didn’t know she was nasty’. I wasn’t referring to she’s nasty. I said she was nasty about me. And essentially I didn’t know she was nasty about me."
He added: "You know what? She’s doing a good job, I hope she enjoys her life… I think she’s very nice."
Mr Trump added that her husband, the Duke of Sussex, “couldn’t have been nicer” when they met on Monday.
He said he congratulated Harry, who recently became a father, calling him a "terrific guy".
The former Ukip leader said the president "really believes in Brexit" and that Mr Trump was "loving his trip to London".
The royal couple were representing the Queen, who held a state banquet to welcome the president to the UK on Monday.
Mr Trump's second UK visit as president was again protested against by thousands but no where near the numbers that attended demonstrations in 2018.
As he did last year, Jeremy Corbyn again spoke to crowds of protesters who took to London's streets on Tuesday, gathering in Trafalgar Square and Parliament Square.
Mr Corbyn refused to attend the banquet on Monday evening and said he stood "in solidarity with those he's attacked in America, around the world and in our own country".
In the GMB interview Mr Trump also spoke about post-Brexit trade deals during the interview, which will be shown from 6am on Wednesday.