North Korean leader Kim Jong-un has said he is committed to denuclearisation, but warned he will change course if the US continues its sanctions.
He made the remarks during his closely-watched annual New Year's address.
Last year's speech set the country on an unprecedented path of international diplomacy with South Korea and the US.
Mr Kim met US President Donald Trump to discuss denuclearisation in June 2018 but with few results so far.
Last year's rapprochement came after a turbulent 2017 marked by North Korea testing missiles that could reach the US mainland and an escalation in rhetoric between Pyongyang and Washington with both sides trading insults and threats of nuclear destruction.
The annual New Year's address is a tradition Mr Kim picked up from his grandfather, Kim Il-sung, founder of the communist country.
The speech is aimed primarily at a domestic audience and, as in previous years, focused largely on the economy - but international observers scan every line for clues to Pyongyang's international agenda as well.
In this year's speech, broadcast on state television early on Tuesday, Mr Kim said, "if the US does not keep its promise made in front of the whole world... and insists on sanctions and pressures on our republic, we may be left with no choice but to consider a new way to safeguard our sovereignty and interests".
The BBC's Laura Bicker in Seoul says this could mean that North Korea is waiting for the US to act in 2019 and unless it does, the current pause on nuclear weapons testing could be over.
North Korea is subject to various sets of United Nations Security Council sanctions related to its banned nuclear and ballistic missile weapons programmes.
Mr Kim said that North Korea had already pledged not to make, use or spread nuclear weapons and had taken concrete steps to implement this.
He also said he was ready to meet Mr Trump again at any time.
"The tone was what many had expected," Oliver Hotham of news site NK News, told the BBC.
"In all, a speech that boosts his standing at home on key issues while sending a conciliatory but firm message to the US, all the while continuing to woo Seoul with the prospects of renewed cooperation."
It was in last year's New Year's message that Mr Kim announced North Korea would take part in the Winter Olympics hosted by the South, which led to a thaw in relations.
After a flurry of diplomatic activity, in April Kim Jong-un met South Korean President Moon Jae-in for a summit at the inter-Korean border.
They met twice more after that, but the most historic summit of 2018 was the North Korean leader's meeting with US President Donald Trump in Singapore in June.
In the first meeting between a North Korean leader and a sitting US president, the two signed a vaguely-phrased agreement to improve ties and work towards denuclearisation.
Since the Trump-Kim summit though, less progress has been made than at least optimists had been hoping for.
While the North has stopped missile and nuclear testing, there's been little indication that Pyongyang is working towards complete and verifiable denuclearisation as the US has called upon it to do.
The North has dismantled some testing facilities but there are allegations it is continuing its weapons programme.
President Trump has said he expects a second summit to take place as early as February, but there has been no confirmation yet.
There are also plans for Kim Jong-un to travel to the South's capital Seoul for another inter-Korean summit but again, those plans have not been confirmed yet.