North and South Korea signalled a surprise thaw in relations on July 27, announcing the restoration of cross-border communications that were severed more than a year ago and an agreement between their two leaders to improve ties.

The joint announcement, which coincided with the anniversary of the end of the Korean War, was the first positive development since a series of summits between the North’s Kim Jong-un and the South’s President Moon Jae-in in 2018 failed to achieve any significant breakthrough.

The two sides revealed that Kim and Moon had exchanged a series of letters since April in which they agreed that re-establishing hotlines would be a productive first step in rebooting relations between the two rivals who, despite the end of their 1950-1953 conflict, remain technically at war.

“The top leaders of the north and the south agreed to make a big stride in recovering the mutual trust and promoting reconciliation by restoring the cut-off inter-Korean communication liaison lines,” the North’s official Korean Central News Agency (KCNA) reported.

Pyongyang unilaterally cut off all official military and political communication links in June last year over activists sending anti-Pyongyang leaflets across the border, but the two sides said all lines were restored on July 27.

They exchanged their first phone call since the suspension on the morning of July 27, Seoul’s unification ministry said, with the defence ministry adding that military hotlines were also back to normal operation.

Moon’s office said restoring the hotlines was the first step towards improving ties. “The two leaders also agreed to restore mutual trust between the two Koreas as soon as possible and move forward with the relationship again,” it added in a statement.

The dovish Moon is credited with brokering the first-ever summit between North Korea and a sitting US president in Singapore in June 2018.

But Pyongyang largely cut off contact with Seoul following the collapse of a second summit between Kim and then US president Donald Trump in Hanoi that left nuclear talks at a standstill.

Just days after severing the hotlines last year, Pyongyang also blew up an inter-Korean liaison office on its side of the border and threatened to bolster its military presence along the Demilitarised Zone that separates them.

The US welcomed the agreement.

“We certainly believe that this is a positive step,” Department of State spokeswoman Jalina Porter told reporters.

“Diplomacy and dialogue are central to achieving complete denuclearisation and establishing permanent peace on the Korean peninsula,” she said.

Since US President Joe Biden took office, Pyongyang and Washington have adopted a wait-and-see attitude to relations following the diplomatic roller-coaster ride under Trump that produced three summits but no agreement on dismantling the North’s nuclear arsenal.

Kim last month said Pyongyang needed to prepare for both “dialogue and confrontation” with Washington – but with a particular emphasis on the latter.

The White House promised a “practical, calibrated approach” – including diplomatic efforts – in a recent review of its strategy to persuade the impoverished North to give up its nuclear weapons and missile programmes.

Sung Kim, the top US diplomat in charge of North Korea negotiations, last month said Washington was ready to meet with Pyongyang “anywhere, anytime, without preconditions”.

But Kim Yo-jong – Kim Jong-un’s sister and one of his key advisers – dismissed the offer.