Media playback is unsupported on your device Media caption The US said North Korea could not talk its way out of sanctions

The US and South Korea have responded coolly to North Korea's offer of high-level talks with Washington.

North Korea will be judged "by its actions and not its words", a US spokeswoman said.

The North proposed talks on "regional peace" with the US on Sunday, but said there should be no "preconditions".

Last week, planned talks between Pyongyang and Seoul fell through following disagreement over which delegates should attend.

Regional tensions were raised earlier this year after Pyongyang conducted its third nuclear test and threatened to attack South Korean and US targets in the region.

'Actions not words'

In recent weeks rhetoric from Pyongyang has softened, but US officials appeared sceptical of its offer.

Timeline: Korean tensions 12 Dec: North launches a rocket, claiming to have put a satellite into orbit

North launches a rocket, claiming to have put a satellite into orbit 12 Feb: North conducts underground nuclear test

North conducts underground nuclear test 11 Mar : US-South Korea annual military drills begin

: US-South Korea annual military drills begin 30 Mar: North says it is entering a "state of war" with South

North says it is entering a "state of war" with South 2 Apr: North says it is restarting Yongbyon reactor

North says it is restarting Yongbyon reactor 3 Apr: North blocks South workers from Kaesong industrial zone, then on 9 Apr pulls its workers out

North blocks South workers from Kaesong industrial zone, then on 9 Apr pulls its workers out 26 Apr : Seoul announces withdrawal of all remaining South Korean workers from Kaesong

: Seoul announces withdrawal of all remaining South Korean workers from Kaesong 2 May: North Korea jails US man for 15 years

North Korea jails US man for 15 years 22 May: North Korea sends envoy to China

North Korea sends envoy to China 10 June North and South agree to top-level meeting in Seoul; talks are arranged but then scrapped What does Pyongyang want?

"Our desire is to have credible negotiations with the North Koreans, but those talks must involve North Korea living up to its obligations to the world, including compliance with UN Security Council resolutions, and ultimately result in denuclearisation," US National Security Council spokeswoman Caitlin Hayden said.

North Korea had to live up to its obligations on nuclear proliferation, Denis McDonough, chief of staff to the US president, told US broadcaster CBS news.

"We'll judge them by their actions, not by the nice words that we heard yesterday," Mr McDonough said.

"They're not going to be able to talk their way out of very significant sanctions they're under now," he added.

North Korean shifts from threat to dialogue are familiar fare to Washington, the BBC's Lucy Williamson in Seoul reports.

North Korea's powerful National Defence Commission had also suggested that any talks on reducing nuclear weapons would need to include American weapons as well as North Korean ones, our correspondent adds.

South Korea's Unification Ministry said its stance on talks was the same as the US.

"The window of dialogue is open but that the North should take concrete steps first," ministry spokesman Kim Hyung-seok said.

North Korea has reneged on deals with the US on several occasions in the past. In February 2012, it agreed to a partial freeze in nuclear activities and a missile test moratorium in return for US food aid.

However, it announced plans for a rocket launch in March that year - something the US called a disguised test of banned missile technology - leading the US to suspend its plans for food aid.

The US, Japan and South Korea are scheduled to meet in Washington on Wednesday to discuss resuming six-party talks on nuclear disarmament with North Korea.

The six party talks are the agreed forum for discussing North Korean denuclearisation, but have been stalled since 2009.

The US also wants a commitment to denuclearisation to be a precursor to negotiations with North Korea.