The last white leader of South Africa FW de Klerk has warned US President Donald Trump that he is not doing the free world any favours by sending overzealous tweets.
The former president, who freed Nelson Mandela and oversaw the end of apartheid in the 1990s, accused Mr Trump of overreacting on the North Korea missile testing crisis.
The Nobel Peace Prize winner said he had been prepared to give President Trump a chance.
"If he did the right thing I'm still prepared to give him a chance but I am critical of his overzealousness at tweeting," Mr de Klerk said.
"He's, I think, not taking the big issues seriously enough with all these tweets.
"At times he's pouring oil on fire instead of putting the fire out and stepping back a while before he commits in a more organised and structured way."
Mr de Klerk was in Dublin with the Global Leadership Foundation, an organisation he set up to bring together statesmen and women and former leaders to privately advise governments in developing countries.
He added: "I think he's not doing the free world a favour by the way in which he's acting."
Mr de Klerk toured EPIC the Irish Emigration Museum in Dublin, before addressing a small group of invited guests and discussing global issues.
On Brexit, Mr de Klerk said he was in the remain camp and that European leaders should have done more to give former British prime minister David Cameron concessions ahead of the 2016 referendum.
"They should have helped David Cameron by making some concessions," he said.
"By limiting, not stopping, limiting the freedom of movement of people, by recognising the right of the supreme position of Britain lawfully.
"I think it was achievable.
"I think it's sad. I'm worried about what effect there will be on London's place as the (top) business place almost, one of the (top) business places in the world and the effect it may have on the city."