Leader Kim Jong-un said he is willing to discuss giving up nuclear weapons if the safety of his country could be guaranteed.
However, experts warned even if North Korea freezes missile tests during the talks, they could still be getting ahead with technical work and simply using it as a stalling tactic.
Some officials in Washington told Reuters news agency they are using the talks as a way to buy time to avoid international sanctions while developing weapons in the background.
The despot Kim has agreed to refrain from conducting nuclear and missile tests while engaging in dialogue with South Korea.
The hermit state has tested dozens of missiles of various types in the past two years, which has included a ballistic missiles capable of hitting anywhere in the United States.
This work could include completing a vehicle that can deliver a nuclear weapon, the production of rocket frames and increasing the output of plutonium and uranium for bomb-making.
Nuclear non-proliferation expert, David Albright said: “North Korea can be expected to proceed on all these things unless an agreement freezes or stops these activities, something unlikely in the short run.”
A senior fellow at Washington’s US-Korea Institute, Joel Wit, said: “These programs are going to continue, but if we have a suspension of nuclear tests and missile tests, that’s a good first step here. It’s better than not having one.”
Some US officials, who wished to remain anonymous, said President Trump would cease the diplomatic talks if North Korea simply tries to drag them out.
They said the Trump administration must weigh up risks before going to the negotiating table.
Mr Trump tweeted on Tuesday: “Possible progress being made in talks with North Korea. For the first time in many years, a serious effort is being made by all parties concerned.
“The world is watching and waiting! May be false hope, but the US is ready to go hard in either direction!”
South Korea President, Moon Jae-in, said yesterday: “Because denuclearisation is our final goal, it may be difficult to move all once toward denuclearisation. What is possible is to agree on a path through different road maps to achieve denuclearisation.”
The announcement of the talks has been seen as a diplomatic accomplishment for President Moon, who used the Winter Olympic Games to try and improve relations with North Korea.