Obama to meet South Korea's Park Geun-hye in May
US President Barack Obama will meet South Korean President Park Geun-hye in Washington on 7 May amid high tensions on the Korean peninsula.
The meeting will cover economic and security issues, officials say.
In recent weeks, the North has threatened to attack South Korea, Japan and US bases in the region.
The North has now said it will retaliate against the South after protesters there burned portraits of its leaders.
Tensions have been high on the Korean peninsula since North Korea conducted its third underground nuclear test on 12 February, which resulted in sanctions from the UN.
Talks between Mr Obama and Ms Park would touch on "continued co-operation on denuclearisation of the Korean peninsula and countering the North Korean threat," a statement from the White House on Monday said.
"They will also review the progress made in strengthening our economic ties and in enhancing and modernising bilateral security co-operation," the statement added.
Ms Park's scheduled talk with Mr Obama follows a meeting with US Secretary of State John Kerry, who was in Seoul on 12 April as part of his tour of Asia.
She was elected in December and assumed office on 25 February.'Ultimatum'
The announcement of the meeting came a day after North Korea marked the 101st anniversary of the birth of founding father Kim Il-sung.
Protesters in South Korea's capital, Seoul, burned portraits of Kim Jong-un, his father Kim Jong-il, and grandfather Kim Il-sung on Monday.
In response, North Korea through its official news agency KCNA issued an "ultimatum" against the South if it did not apologise for the protests.
"Our retaliatory action will start without any notice," KCNA said.
"The military demonstration... will be powerful sledge-hammer blows at all hostile forces hurting the dignity of the supreme leadership," it added.
South Korea's defence ministry said the North's ultimatum was "regrettable" and that its provocations were "illegal".
"We will retaliate thoroughly and resolutely to provocations staged for any reasons," the ministry's spokesman, Kim Min-seok, said.
Meanwhile, North Korea's ambassador to the UK, Hyon Hak-bong, said that his country was not the cause of current tension on the peninsula but was only responding to US aggression.
He told Britain's Marxist-Leninist Communist Party in a rare speech that North Korea was penalised even after following international norms over its banned satellite launch on 12 December.
He said North Korea was facing a "grave situation", with 200,000 US troops staging drills in the South and warnings from both countries of a military response to any provocation.
While Mr Hyon's stance is not new, the fact that he spelled out his government's position in public like this is striking, says the BBC's Lucy Williamson in Seoul.
North Korea on Monday rejected calls for talks by the US and South Korea, but its rhetoric does appear to have lessened recently, and regional fears of a missile launch have so far not been realised, our correspondent adds.
A heightened state of vigilance has been in place for the past few days in South Korea, with the country's defence ministry saying that the North could still test fire an intermediate range missile.
There was speculation that the North would use Kim Il-sung's birth anniversary for a missile launch, following reports that it had moved at least two Musudan ballistic missiles to its east coast.
But the celebration was relatively quiet. North Korean leader Kim Jong-un marked the occasion with a visit to his grandfather's mausoleum, KCNA says.
He also attended basketball and volleyball games between military academies, which state media call "anti-American games", and watched a concert, it added.
Kim Il-sung died in 1994, and was succeeded by Kim Jong-un's father Kim Jong-il, until his death in 2011.