North Korea accepted Russia's invitation, but Russia is waiting on Pyongyang to make the official announcement about the May trip, the official said. This would mark Kim's first official foreign trip since inheriting the leadership in late 2011.
"The invitation was sent to Kim Jong Un. North Korea
accepted the invitation. The leadership of North Korea is expected to take part in Victory Day celebrations in Moscow," the Russian official said.
So far, North Korean state media has not issued any statement about the invitation.
This year's Victory Day marks the 70th anniversary of the Soviet Union's victory over Nazi Germany in World War II.
Chatter over whether Kim would make his first official overseas trip during the pivotal anniversary started in late December after Russian state media reported that Moscow had extended an invitation to Pyongyang.
On December 22, Russian presidential aide Yuri Ushakov told Itar-Tass
: "First signals are given from Pyongyang that the North Korean leader plans to come to Moscow and attend celebrations."
and North Korea have been fostering warmer relations.
If Kim appears in Russia along with other world leaders, he may look like a minor figure, said Dr. Leonid Petrov, an Asian studies professor who specializes in the political history of North Korea.
"In a setting with a large crowd of state officials, in group pictures, he would look like a minor figure instead of what he's portrayed in North Korean media as supreme leader, invincible marshal, jack of all trades.
"So I think if Kim Jong Un decides to go to Moscow, he's going to look like a very lonely, lonely figure."
The Kremlin has invited 68 world leaders to its Victory Day celebrations on May 9, said Russian Foreign Minister Sergey Lavrov as quoted on Russian network RT.
He was quoted in Russian media as saying that Chinese President Xi Jinping
will also attend.
Russia and North Korea
In the last year, Russia and North Korea, two historical allies, have increasingly established stronger ties as Russian President Vladimir Putin
faces international backlash over the war in Ukraine
. The two countries declared 2015 their "Friendship Year."
Both countries have been slapped with sanctions by the United States and are facing international isolation.
"North Korea is a convenient friend for Moscow -- it's anti-American and it's in a key place of Asia," Petrov said. "Russia lost many of its traditional allies -- it needs friends, both economically, politically, strategically."
Ties between North Korea and Russia date back to World War II, when Kim Jong Un's grandfather and founder of the country, Kim Il Sung, trained as a communist guerrilla leader in the Soviet Union. Throughout Kim's subsequent reign, the Soviet Union backed the nation. After the Soviet Union crumbled in the early 1990s, North Korea became increasingly reliant on China.
Kim's father, Kim Jong Il, visited Moscow several times, with his last visit in 2011. The late Kim rode into Russia in an armored train (he disliked flying) and met with both Putin and Prime Minister Dmitry Medvedev
"Moscow undertook a diplomatic offensive" with North Korea, said Petrov, of Australian National University. "It absolved $10 billion of Soviet-era debts from the account books and started rebooting relationships between North Korea and Russia."
Last year, Russia forgave 90% of North Korea's $11 billion debt.