However he said there's a difference between having the ability to fire a single nuclear missile and the capability of producing large amounts of material and developing an arsenal of such weapons.
During the same conference, US President Donald Trump's National Security Adviser HR McMaster said the country was in a race to resolve the crisis.
"We are not out of time," he told the forum, organised by the Foundation for Defense of Democracies think tank.
"But we are running out of time," he said.
'Backed into a corner'
It comes as Russia called for support for a plan between Moscow and Beijing to end US and South Korean military drills in exchange for North Korea halting its missile testing.
Foreign Minister Sergei Lavrov said a dialogue would prevent a huge humanitarian, economic and ecological catastrophe in the region.
Russian President Vladimir Putin has also repeated his calls for calm.
While condemning Pyongyang's nuclear ambitions, Putin said the stand-off should be settled through dialogue and without "cornering North Korea, threatening to use force or going down to outright boorishness and swearing."
Speaking to international policy experts at the Valdai forum in Sochi, Putin criticised the US and its allies for missing a chance to build a safer and more stable world after the Cold War.
Last month, Putin said the tense standoff between North Korea and the United States was on the verge of a big conflict.
He also said it was a mistake to try and pressure Pyongyang over its nuclear missile program.
"It is essential to resolve the region's problems through direct dialogue involving all sides without advancing any preconditions (for such talks)," Putin wrote on an article posted on the Kremlin's website.
"Provocations, pressure, and bellicose and offensive rhetoric is the road to nowhere."
North Korea is working to develop a nuclear-tipped missile capable of hitting the US and has threatened to fire missiles near the US Pacific territory of Guam.
Trump and North Korean leader Kim Jong-un have been engaged in a dramatic war of words in recent months after Pyongyang conducted several missile tests.
North Korea also conducted what it claimed was a successful test of a hydrogen bomb on August 3, sparking global condemnation.