The Prime Minister said that he would “not get involved” in the US election after previously criticising Mr Trump for his comments on banning Muslims from America.
Mr Cameron has previously described Mr Trump as “stupid, divisive and wrong”.
However, speaking at the G7 Summit in Japan, Mr Cameron said: “I would congratulate anybody who can get through those marathon processes for leading one of the two great political parties in the United States of America. It is an extraordinary marathon.
“When I think of the campaign I held in 2005, touring the UK to become leader of the Conservative Party it was pretty exhausting – but it is a small campaign compared to the vast nature of what these candidates have been through. So anyone who gets through that gets my congratulations.”
Mr Cameron confirmed that he will meet Mr Trump if, as is expected, he visits the UK before the American election.
In the wake of Mr Trump’s comments about Muslins, the Prime Minister said that if he came to the UK, the country would “unite” against him.
However, when asked if he stood by those comments, Mr Cameron said: “I’m not going to get involved at all in the American election – it’s a matter for the American people to choose their next President. I believe in the special relationship. I believe the special relationship will work whoever is in whichever jobs in the UK or in the US – it’s a shared interest about values and about security and prosperity in our world.”
Cameron: Britain would survive after leaving EU
Britain will “find our way” even if the country votes to leave the European Union, David Cameron has said.
The Prime Minister said that the UK is “an amazing country” and will flourish “whatever the British people choose” in the referendum.
Mr Cameron also denied he was a “closest Brexiteer” after his friend and former No 10 aide Steve Hilton claimed he previously supported leaving the EU.
His comments, made at the G7 summit in Japan, come after a series of dire warnings about the impact of a Brexit on the British economy.
In recent weeks Mr Cameron has said that leaving the EU would cause a recession and see the value of British homes plummet.
However, when asked if he stands by comments made last year that “Britain could thrive” outside the EU, Mr Cameron said: “I withdraw absolutely nothing I’ve previously said. Britain is an amazing country. We can find our way whatever the British people choose.
“But the question for us is not are we a great country, have we got a brilliant economy, have we got talented businesses, have we got great entrepreneurs, have we got amazing universities, brilliant scientists? Can we go on as we have in the past, breaking new boundaries in all these areas? The question is how do we do best?
“It’s not just me saying that there are economic risks from Britain leaving the EU. It is now a pretty large consensus that includes people of impeccable independence and academic standing.”
Mr Cameron also admitted that Thursday’s migration figures were “disappointing”.
However, he said that a Brexit is not the answer because it would “wreck the economy”.
Asked if he is a “closet Brexiteer” following claims by Steve Hilton, the former Downing Street aid who said Mr Cameron would vote to leave if he was not the Prime Minister, Mr Cameron said: “I am not a closet anything. I have pretty much had the same view about Europe ever since I got involved in active politics,” said Mr Cameron.
“I have always taken the same view, which is that we are better off in this organisation but we should be aiming to reform this organisation, we should be looking to enhance the special status that Britain.
“I have never been a closet Brexiteer. I am absolutely passionate about getting the right result, getting this reform in Europe and remaining part of it. It’s in Britain’s national interest.”
Cameron reacts to EU migraition stats
David Cameron has suggested that “disappointing” record migration figures are a price worth paying for staying in the European Union and not “wrecking the economy”.
The Prime Minister he “does not believe for one minute” that controlling immigration by leaving the EU would be the right thing to do.
It came after figures on Thursday disclosed that net migration to the UK has risen to 330,000, the second highest level on record.
The key measure – the difference between the number of people arriving and leaving the country – was estimated at 333,000 for the year ending December 2015.
This is 3,000 short of the all-time high posted last year, 10,000 higher than the figure published for the 12 months to September, and three times the Government’s target level.
Asked about the figures,Mr Cameron said: “Of course the figures yesterday are disappointing. “They come at a time when Britain has created record numbers of jobs.
It’s important to remember that there are record numbers of British nationals in work, record numbers of British women in work, that nine out to 10 people working in our economy are Brits.”
The Prime Minister criticised Vote Leave campaigners who advocate controlling Britain’s borders by quitting the EU.
He said: “Let me say this to those who want to leave the single market and cause all the damage that would do to jobs and to growth and to investment. “I do not believe for one minute that the right way to control immigration is to wreck our economy. That is the consequence of leaving the single market, inevitably alongside years of uncertainty as we try to work out what our relationship would be with the EU.”
Merkel: No Brexit discussion at G7 meeting
The comment came after Angela Merkel said Britain’s EU referendum was not formally discussed at the G7 meeting of the world’s most powerful leaders.
The German Chancellor said that Brexit was “no subject here” when asked if she and the other leaders of the world’s major economies discussed the issue.
It is believed that the referendum was discussed briefly on the margins of the meeting, but it was not a central issue during the summit in Japan.
The G7 did include a brief warning about the economic risk of a Brexit in its 32-page declaration at the end of the summit.
UK exit from the EU would reverse the trend toward greater global trade, investment and the jobs they create and is a further serious risk to growth,” warned the final declaration,
However the remarks by the G7 leaders will be certain to intensify the controversy over outside political figures trying to influence Britain’s EU referendum which takes place next month.
However, it emerged on Friday that the warning about a Brexit was not included in a draft of the declaration released on Thursday and was only a last-minute addition.
The warning about an EU exit in the final declaration said: “A UK exit from the EU would reverse the trend towards greater global trade and investment, and the jobs they create and is a further serious risk to growth.”
Asked about any discussions about the issue of a Brexit, Mrs Merkel said: “It was no subject here. But there was the signal that all who sat here want Britain to stay part of the EU.”