SEOUL, South Korea — The South Korean entrepreneurs who invested up to 10 years and millions of dollars in the Kaesong industrial complex, a symbol of economic collaboration between the rival Koreas that is now shuttered by the North, have little more than hope to cling to as assembly lines sit idle day after day.

They say they want to go back to work. The sooner the better. They say they cannot abandon their investments in factories, or the cheap North Korean labor that helped them put aside misgivings about doing business with the South's unpredictable neighbor. Some were just getting over their beginners' mistakes, and were starting to see the fruits of their work.

But North Korea has been unrelenting in its decision to bar South Koreans from entering the factory city just inside its border, and withdraw the 53,000 North Korean workers who manned assembly lines. As the lockout enters a third week, customers of the South Korean companies are growing impatient and losses are mounting. Some businesses are already quietly mulling giving up on Kaesong altogether.

"We have built the Kaesong industrial complex by the sweat of our brows, believing in guarantees that we would be able to work freely," said Han Jae-kwon, chief of the group of South Korean factories in Kaesong. "We find the reality tragic and sad that we are unable to travel to our own factories."

The Kaesong complex has been nearly deserted since early April, when Pyongyang pulled the plug on its last significant economic link with the South. Most of the nearly 900 South Korean managers and entrepreneurs left soon after. About 200 remain and are getting by on whatever food they had stored.

The shutdown was punishment for Seoul's ongoing joint military drills with the United States that have incensed Pyongyang because it sees the exercises as a rehearsal for an invasion. Restricting travel through the heavily armed border is also a way to remind South Koreans that a state of war hangs over the Korean Peninsula, 60 years after the Korean War ended with a truce.