Prince Charles meets Barack Obama at White House
The Prince of Wales has discussed energy and environmental issues with US President Barack Obama in Washington.
The meeting in the White House's Oval Office comes ahead of the president's state visit to the UK later this month.
Mr Obama also said he was impressed how the Duke and Duchess of Cambridge handled the pressure of their wedding.
Earlier, the prince made a keynote speech at a conference on sustainable agriculture and attended an event in support of UK and American troops.
The White House talks came at the end of Prince Charles's two-day visit to Washington.
The pair last met in France in 2009 during the 65th anniversary commemorations for the D-Day landings.
Mr Obama was not a guest at the royal wedding at Westminster Abbey on 29 April but he told Charles the occasion had mesmerised the US.
He went on to joke that he could not have coped with the pressure of such a situation himself.
The conversation then turned to the military and Charles revealed how he was worried when Prince Harry served for 10 weeks as a forward air controller in Afghanistan.
In a statement, the White House said: "President Obama warmly welcomed the prince's work over three decades on environmental issues, halting deforestation and encouraging sustainable food production.
"The president also congratulated the prince on the wedding of his son, Prince William, to Catherine Middleton and extended his best wishes to the newlywed couple."
Mr Obama also affirmed "the strength and depth of the alliance" between the US and UK and said British troops had made "important contributions" to action in Afghanistan and Libya.
Earlier, in his address to the Future of Food conference at Georgetown University, Prince Charles called on more governments and companies to support organic food production.
He said had spent more than 30 years speaking on the topic of food production in an effort to ensure the health of future generations and "the integrity of nature itself".
"The world is gradually waking up to the fact that creating sustainable food systems will be paramount," he said.
He added: "Soils are being depleted, demand for water is growing ever more voracious and the entire system is at the mercy of an increasingly fluctuating price of oil."
Referring to the need for better "food education", the prince went on to praise First Lady Michelle Obama's campaign which aims to tackle childhood obesity in America.
And he made a brief reference to Prince William's marriage, telling the audience that talking about organic farming was "a change from making embarrassing speeches about my eldest son during wedding receptions".
Charles met US military veterans at the event to celebrate the work of the British Forces Fund and America's United Service Organisations - two bodies which organise morale-boosting entertainment for troops on both sides of the Atlantic.
The prince highlighted how both the UK and US owed an "immense debt" to their armed forces who were prepared to risk their lives serving in Afghanistan.
"As far as I'm concerned, nothing is too good for our servicemen and servicewomen," he said.
He then went on to recite a few lines from Gilbert and Sullivan's Pirates of Penzance operetta.
More speaking than singing, he quoted from the song Oh Better Far to Live and Die: "When I sally forth to seek my prey, I help myself in a royal way, I sink a few more ships, it's true, than a well-bred monarch ought to do."
On Tuesday, Charles visited the Common Good City Farm, located on a former baseball field in a deprived area of the city.
Prince Charles met staff and volunteers at the site where fruit, vegetables and flowers are grown.
The prince also attended a Marshall Scholar alumni reception at the US Supreme Court.
He is an honorary patron of the Association of Marshall Scholars, which funds Americans to study at UK universities in recognition of the post-war European recovery Marshall Plan programme.