The US president and his wife welcomed 21,000 children and adults to the White House on Monday to take part in the traditional Easter Egg Roll, which takes place every year.

Read: 5 things you probably didn't know eggs can do

Addressing the crowd from a balcony before blowing the whistle on the event - which is one of the biggest social occasions of the White House year - Trump thanked wife Melania for "working on this for a long time to make it perfect."

He went on to praise the efforts of his government in pursuing its policy objectives.

"This is the 139th Easter Egg Roll. Think of it, 139. And we will be stronger and bigger and better as a nation than ever before. We're right on track," he said.

In less than 100 days as leader, Trump has suffered from several setbacks including legal challenges to his initial ban on travelers from Muslim-majority countries. A second ban is also facing legal challenges. Last month, his effort to repeal the Affordable Healthcare Act (Obamacare) was shot down by rebel Republican lawmakers.

'Gotta behave'

The new president has, however, earned plaudits in some quarters for taking a tougher policy line on Syria, with the firing of 59 Tomahawk missiles at a Syrian air base earlier this month. The action, which has caused some tension with Russia, came in response to a chemical attack widely blamed on government forces which killed nearly 90 people.

Leaving the event, Trump was asked about his message for North Korean leader Kim Jong Un at a time of heightened tensions on the North Korean peninsula. The president responded, "Gotta behave."

There were murmurs among observers ahead of the egg roll, as Melania nudged the president during the national anthem when he appeared to forget to put his hand on his heart.