As pressure over North Korea's nuclear weapons program grows, the most valued Arab allies to the United States host thousands of its laborers, whose wages help Pyongyang evade sanctions and build the missiles now threatening the US and its Asian partners, officials and analysts say.

From state-run restaurants to construction sites, North Korean workers in Kuwait, Oman, Qatar, and the United Arab Emirates face conditions akin to forced labor while being spied on by planted intelligence officers, eating little food, and suffering physical abuse, authorities say.

North Korean laborers even have helped expand a UAE military base that hosts US forces fighting the Islamic State group, two officials familiar with Pyongyang's tactics told The Associated Press.

Emirati officials, who are now relying on South Korean expertise to build the first nuclear power plant on the Arabian Peninsula, did not respond to requests for comment.

"To put it fairly simply – an isolated country like North Korea is always seeking hard currency," said Giorgio Cafiero, the chief executive officer of the Washington-based political risk consultancy Gulf State Analytics. "The Gulf is a place that the North Koreans see as a very reliable place to make the money."

Longstanding international concerns over North Korea's nuclear weapons program have intensified since it conducted two nuclear tests last year and launched its first intercontinental ballistic missile July 4.

Facing US and international sanctions, North Korea has relied on its overseas laborers to get cash. China and Russia are its biggest markets, but the Gulf hosts thousands.

Go Myong-Hyun, a research fellow at the Asan Institute for Policy Studies, said some Middle East countries like North Korean workers because "they don't run away."

Across the Gulf, some 6,000 North Koreans work, two officials familiar with Pyongyang's tactics told the AP, including 2,500 in Kuwait, as many as 1,500 in the UAE, and 2,000 in Qatar. The officials spoke on condition of anonymity to discuss confidential intelligence reports.

Most North Koreans working in the Gulf earn around $1,000 a month, but the North Korean government keeps about half and another $300 goes toward construction company managers, the officials said. That leaves workers with just $200.

In the UAE, eight North Korean workers typically live together in a 69-square-foot space and eat little food, the two officials said.

North Korea also operates three Korean restaurants in the UAE – two in Dubai and one in Abu Dhabi – out of an estimated 130 it runs around the world, the officials said. The two officials said another 1,000 North Korean workers will arrive in the UAE in the coming months.

Typically, those in construction work as subcontractors, with those commissioning the projects sometimes unaware they have North Koreans working on site, the officials said.

They suggest that may have been the case when North Korean workers took part in a recent expansion of the UAE's Al-Dhafra Air Base, a major Emirati military installation outside Abu Dhabi and home to some of the 5,000 American troops stationed in the country.

Maj. Josh T. Jacques, a spokesman for the US military's Central Command, which oversees the Middle East, said its policies do "not allow for the admittance or contracting of North Korean nationals and other countries of interest at any US military installation."

"We are not aware of any North Korean laborers at Al-Dhafra Air Base and we would certainly be concerned if there were," he told the AP.

America and others have been pushing its Gulf partners to limit their exposure to North Korea. A bill passed Tuesday by the House of Representatives includes limits on the use of overseas North Korean labor.

In Oman, the sultanate expelled 300 North Koreans working in the country in December, according to South Korea. Some 80 are believed to remain. In Qatar, the United Nations said one construction company dismissed 90 North Korean workers in 2015 over abuse and labor law violations that included an incident that killed one laborer.

North Korea's sole embassy for the region is in Kuwait City, where authorities in 2016 stopped direct flights by the country's state-run Air Koryo and ceased issuing new worker visas. Embassy officials there and authorities in Kuwait did not respond to requests for comment.

Oman's Embassy in Washington simply said "it's the first time we hear of" North Korean workers being expelled from the sultanate, without answering any questions.

In a statement to the AP on Friday, Qatar acknowledged "a few companies" had contracted North Korean workers, but that it stopped issuing visas to them in 2015. Qatar said "less than 1,000 remain" in the country and their visas will not be renewed.

"Qatar is in compliance with all UN sanctions against North Korea," the statement said. "There have never been workers from North Korea working on any World Cup construction sites."

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Today, Gulf nations keep their ties with North Korea largely quiet while supplying oil and natural gas crucial to the economies of Pyongyang adversaries South Korea and Japan. Given that, as well as their close defense ties to the US, Gulf nations likely would side against North Korea if given a firm enough push, Cafiero said.

"The Arab Gulf states would have a lot to lose if there was a conflict," he said.