North and South Korea held fresh talks on Wednesday about reopening their jointly-run industrial estate, but little progress was reported as they wrangled over who was to blame for the shutdown.

The Kaesong estate in North Korea, the last remaining symbol of cross-border cooperation, shut down in April as military tensions mounted after the North’s February nuclear test and South Korean-US war games.

Dialogue resumed in recent weeks but three previous rounds of talks this month on Kaesong ended in deadlock.

“The weather is not so bad today. Do you think we will have good results today?” the North’s chief delegate Pak Chol-Su said at the start of Wednesday’s talks, the fourth round.

“I hope we’ll be able to build a house that can withstand any gusts of wind or pouring rains,” his South Korean counterpart Kim Ki-Woong replied, according to media pool reports.

Following a meeting attended by all three delegates from each side, Pak and Kim met separately a few more times. But there were no signs of them narrowing differences.

The morning discussions appeared to be a repeat of previous rounds, with each side refusing to budge on conditions for resuming operations at the estate, built after a landmark inter-Korean summit in 2000.

The South urged the North to promise not to cause another closure and to take a respectful and constructive position to resolve the issue, according to an official with Seoul’s unification ministry.

However the North reiterated its previous position that operations at the zone should be normalised as soon as possible, she said.

Kaesong was previously a valuable source of hard currency for the impoverished North.

At a meeting earlier this month, the two sides agreed in principle to reopen the estate, where 53,000 North Koreans worked in 123 South-owned factories producing textiles or light industrial goods.

But little progress has been made since then amid squabbles over which side should take responsibility for the suspension, and Pyongyang’s refusal to accept Seoul’s demand for firm safeguards against another unilateral shutdown.

Seoul also wants to allow foreign firms to operate in Kaesong in an apparent attempt to make it more difficult for Pyongyang to shut the estate if relations worsen.

The North has called for an unconditional and quick restart, blaming Seoul’s “hostile policy” for the suspension and for the current deadlock in negotiations.

“They kept talking past each other. These can hardly be called negotiations but a dialogue of the deaf,” Chang Yong-Seok, senior researcher at the Institute for Peace and Unification at Seoul National University, told AFP.

Professor Yang Moo-Jin of Seoul’s University of North Korean Studies said both sides feel pressure to achieve some results before the next US-South Korean joint military exercise, Ulchi Freedom Guardian, takes place next month.

The North needs to satisfy a US demand that it improve ties with Seoul before any talks with Washington.

Seoul meanwhile will be seeking to cool tensions ahead of the military exercise, which if left unchecked could smother new President Park Geun-Hye’s policy of measured trust building in its infancy, Yang said.

“Both leaders of the two sides are taking a strong hands-on approach, meddling in the talks too intrusively, leaving their delegates little room to wiggle at negotiations,” Yang said.

Kaesong was the most high-profile casualty of the months of friction that followed the North’s third nuclear test in February, the subsequent tightening of UN sanctions and the US-South Korean military exercises.

Wednesday’s talks on restarting Kaesong were held at the estate, some 10 km (six miles) inside the North.

Many of the South Korean firms with factories there, facing millions of dollars in damages due to the shutdown, have threatened to leave the complex permanently if the suspension continues.