Increasingly tough financial sanctions, an arms embargo and other international restrictions on trade with North Korea have significantly delayed expansion of Pyongyang's illicit nuclear arms program, Reuters reported citing a confidential report by a UN panel of experts.

The latest annual report by the UN sanctions-monitoring group comes as the United States seeks to persuade China that applying economic and other sanctions against its neighbor is crucial to halting the program.

"While the imposition of sanctions has not halted the development of nuclear and ballistic missile programs, it has in all likelihood considerably delayed (North Korea's) timetable and, through the imposition of financial sanctions and the bans on the trade in weapons, has choked off significant funding which would have been channeled into its prohibited activities," the 52-page report said, according to Reuters.

The document covers the period up through last month, diplomats said, so it was too early to measure the effect the latest round of UN sanctions adopted in March.

In the report to the UN Security Council's North Korea sanctions committee, the panel also recommended sanctioning three North Korean entities and 12 individuals. It will be up to the 15-nation council whether or not it follows the recommendations.

The panel listed North Korea's February nuclear test and its rocket launches as examples of violations of Security Council resolutions that have increased international concerns about Pyongyang. It was North Korea's third nuclear test since 2006.

Pyongyang is under UN, U.S., European Union and other sanctions, including a UN ban on all arms exports, due to its nuclear weapons program.