SEOUL (REUTERS) - Fresh UN sanctions are unlikely to halt North Korea's nuclear programme given that seven years of previous measures from the world body and more than 50 years of US penalties have failed to dissuade North Korea from trying to develop banned weapons.
Under new leader Kim Jong Un, the North has pursued its nuclear programme even more aggressively, experts in Seoul said.
The 30-year old Kim, in power for just over a year, also seems more willing to shun China, his sole powerful backer, than his father Kim Jong Il was, one of the experts said.
The UN Security Council is set to agree another round of sanctions against North Korea later on Thursday in response to Pyongyang's latest nuclear test on Feb 12, bringing the measures more into line with a tough regime imposed on Iran.
The nuclear test was Pyongyang's third since 2006. It followed a long-range rocket launch in December. Both tests showed the North had made progress in developing a missile with a test range of 10,000 km and miniaturising a nuclear warhead for it.
"They will never give up their (nuclear) intercontinental ballistic missile plans. Their stance on this is very firm,"said Mr Kim Yeon Su, professor of the department of security policy studies at the National Defence University in Seoul.
North Korea has used its nuclear programme vigorously since Kim Jong Il's regime as leverage to bully the international community for money, resources and aid. His son, Kim Jong Un, took little time to continue his father's ambitions, launching a long-range missile just months after the elder Kim died.
China backed the US-led push for the new round of sanctions in the United Nations. It has also supported previous efforts and stood behind condemnations of the North Korean long-range rocket launch in December which breached UN rules.
Mr Kim from the National Defence University said recent ties between North Korea and China had been fragile. He noted there had been a lack of visits to North Korea from senior Chinese officials since the missile launch in December - a contrast to the usual interaction seen during the days of Kim Jong Il.
A Chinese politburo member was also snubbed by Mr Kim Jong Un on a trip to Pyongyang ahead of the December rocket launch and Beijing summoned the North Korean envoy after the nuclear test to express its "strong dissatisfaction" over the test.
Despite the warning from Beijing, North Korea has told China it is ready to push ahead with a fourth and even a fifth test, a top official with direct access to both capitals told Reuters in February.
"Compared to his father ... Kim Jong-un seems to be charting his own path when it comes to China," said Mr Kim of Seoul's National Defence University.
The new UN sanctions aim to put the squeeze on another three North Korean individuals linked to its arms companies or the nuclear programme and also financial transactions that enable it to finance its weapons plans.
Experts who have dealt with North Korea during periods of negotiation with Pyongyang are sceptical as to whether the money flows - in many cases carried by individuals travelling on diplomatic passports, or the proceeds of illegal activities such as counterfeiting or drugs - can be halted.
After being stung in a US Treasury-led raid on a Macau bank in 2005 that impounded more than US$20 million (S$25 million) of Kim Jong Il's cash, the North has split up its bank accounts into smaller sums, making them harder to trace.
"If this new round of sanctions are at the same level as before, they will have very limited impact," said Mr Moon Seong Mook, a retired South Korean general who took part in military talks and summits with the North from 2004 through 2009.
"We can't say the sanctions have had zero effect ... but the sanctions need to make Kim Jong-un realise he cannot carry on this kind of behaviour any longer."
While Iran exports billions of dollars a year of oil that has been targeted by the United States, North Korea produces little of value to the rest of the world apart from minerals destined for China, some low-end garments and tens of thousands of migrant labourers for Russia, China and the Middle East.
Pyongyang does not produce any national statistics.
Iran's merchandise exports were $131.5 billion in 2011, the year before Washington stepped up sanctions. Of those shipments, three quarters were estimated to be oil and gas, which independent experts estimate may now have fallen by more than half.
North Korea by contrast exported just US$1.07 billion in 2012 to South Korea and its exports to China totalled US$2.48 billion, according to estimates from the Korea International Trade Association, released on Thursday.
Even the new UN sanctions will depend on interpretation from member states. The assessment so far of the impact of past UN sanctions shows there has been a limited impact.
"This is because the vagueness of the existing sanctions, the ability of member states to execute sanctions and different standpoints of states on the sanctions will still exist even if new ones are announced," according to a February report by South Korean government think-tank the Korea Development Institute.
Previous sanctions have ranged from calling upon the North to abandon its nuclear arms programme to limiting financial transactions. Separate US measures have banned imports of any kind of North Korean product. The North has been sanctioned by Washington in one form or another since the 1950-1953 Korean War.
As ever, Beijing holds the key. It will have to decide whether to interdict financial transactions, risking instability in the North, and whether it will inspect cargos travelling through its Dalian port, a key gateway to North Korea, as it is obliged to do under the new UN agreement.
China is thought to be harbouring a lump sum of Pyongyang's financial assets, according to numerous experts who study the North, while simultaneously providing the North with funds and resources as its biggest trade partner.
"It all depends on what China says," said Mr Lee Young Hoon, a senior analyst at SK Research Institute in Seoul, who previously worked for the Bank of Korea and a state-run think-tank.
"If they offer only words like before, then (sanctions) will be of little use."
China has said it will back all UN sanctions.