However, this does not mean that Tokyo is distancing itself diplomatically from the world body, they added.
A foreign ministry official said Japan would cut its contribution in 2006, when the UN next reviews the share each member country pays as dues.
"We are aiming for an amount less than we pay now," the official said.
Japan will pay $280 million, or 19.5% of the total dues, in 2004, a close second behind the United States, which is to contribute 22%.
Japan has laid down cooperation with the UN as a pillar of its diplomacy along with the alliance with the US, but there has been growing dissatisfaction among policymakers over what Tokyo sees as an excessive financial burden.
An advisory body to the prime minister said in a November 2002 report Japan should bring down its share to about 15%, although the foreign ministry official said the government had no specific target in mind.
"There is no logic to explain Japan's excessive UN contribution. Japan and Germany are basically having to shoulder what the US, China and Russia ought to be paying. We must seek to bring it down to around 15%, in line with our economic strength"
Japanese government report
Japan is not a permanent member of the UN Security Council, although it pays nearly as much as the US and more than the other permanent members, Britain, France, Russia and China.
"There is no logic to explain Japan's excessive UN contribution. Japan and Germany are basically having to shoulder what the US, China and Russia ought to be paying," the report said.
"We must seek to bring it down to around 15%, in line with our economic strength."
Seeking Council seat
Prime Minister Junichiro Koizumi threw his support behind US President George Bush's decision to go to war in Iraq despite the lack of a clear UN mandate.
Critics said Tokyo had neglected the international body.
But another Japanese official said the planned cut in funding did not signal a change in Japan's policy of putting priority on the UN and seeking a permanent seat on the Security Council.
Japan has long said it deserves a permanent seat on the Council, which can make key decisions on war and peace.
Most UN members agree that the Council should be reformed, but debate has stalled, with most permanent members unwilling to rush to weaken their own positions.
Japan, the world's largest aid donor until 2001, has also cut down on aid to developing nations, faced with its public-sector debt now reaching 140% of gross domestic product (GDP) - the highest among developed economies.
In the draft budget for the fiscal year starting in April, such assistance will be slashed by 4.8% from the previous year to $7.64 billion, a 15-year low.