KUALA LUMPUR (Reuters) – The U.S. Federal Aviation Administration (FAA) has downgraded Malaysia’s air safety rating, restricting the country’s airlines from adding flights to the United States, four sources familiar with the matter and a U.S. government official told Reuters on Monday.

The FAA’s safety rating is based on a country’s aviation oversight regime and is an assessment of the country’s civil aviation authority.

At present, the only Malaysian airline route to the United States is AirAsia X Bhd services from Kuala Lumpur to Honolulu via Osaka.

The Civil Aviation Authority of Malaysia and the FAA did not immediately respond to requests for comment. Malaysia’s transport ministry did not have an immediate comment.

Malaysia has been downgraded to Category 2, said the sources, who did not want to be identified as they were not authorized to speak to the media.

A U.S. government official said the FAA would make an official announcement on Tuesday.

The official said the U.S. government was working with the Civil Aviation Authority of Malaysia and would help the Southeast Asian country achieve international standards that would give it the top Category 1 rating.

Malaysian Prime Minister Mahathir Mohamad said he was not aware of the details of the downgrade.

“If there is anything wrong with our civil aviation authority, we will take measures, we will correct the situation,” he told reporters.

The new rating means Malaysian airlines are restricted to current levels of any existing service to the United States. They would also be subject to additional inspections at U.S. airports.

Under Malaysia’s Category 2 rating, the FAA will also not allow reciprocal code-sharing arrangements between U.S. carriers and Malaysian airlines.

The downgrade places Malaysia in the same FAA category as neighbor Thailand, which was downgraded to Category 2 in December 2015 and has since tried unsuccessfully to restore its Category 1 rating.

Other countries in Category 2 include Bangladesh, Ghana and Costa Rica.

Reporting by Joseph Sipalan, Liz Lee and A. Ananthalakshmi; additional reporting by Rozanna Latiff in Kuala Lumpur and Jamie Freed in Sydney; Editing by Louise Heavens and Muralikumar Anantharaman