Saudi Crown Prince Abdullah Abdul Aziz has sent a letter to Prime Minister Keizo Obuchi to press the Japanese government to build the contentious mining railway in the desert kingdom in exchange for renewal of the oil-drilling rights of Tokyo-based Arabian Oil Co., trade chief Takashi Fukaya said Friday. In the letter, sent late last month and received by Obuchi earlier this week, the prince also pledged Riyadh's intention to keep up its friendly ties with Japan while thanking Tokyo for signing a bilateral agreement on Saudi Arabia's entry into the World Trade Organization. Arabian Oil's oil concession rights expire Feb. 27. Failing to narrow their differences at a meeting Wednesday between Fukaya and the visiting Saudi Arabian petroleum minister, Ali Ibrahim al-Nuaimi, the two sides effectively halted the ministerial negotiations over Arabian Oil's concession rights to the Khafji oil field. , which lies close to the neutral zone between Saudi Arabia and Kuwait. At a regular news conference Friday, Fukaya said he now wants Arabian Oil to do its best to successfully conclude its ongoing negotiations with Saudi Arabia. Arabian Oil President Keiichi Konaga is now back in Riyadh to enter last-ditch negotiations on the issue. In Wednesday's meeting, Fukaya only asked the Saudi minister to consider the latest proposal put forward by Arabian Oil to undertake the 1,400-km railway project, the issue on which governmental talks had foundered. While persisting in demanding that Tokyo build and operate the railway, Riyadh has turned down an investment package of 800 billion yen -- including preferential loans of 140 billion yen -- that Tokyo has offered. Tokyo plans diesel law to cut pollution Tokyo Gov. Shintaro Ishihara unveiled a plan Friday that will oblige all diesel-powered vehicles in Tokyo to be equipped with a device to reduce polluting emissions from April 2006. Fines will be levied on vehicles that do not meet the new requirements, including on vehicles passing through Tokyo from outside as well as those with Tokyo license plates, according to the plan. City officials hope the scheme will be presented to the metropolitan assembly as part of amendments to the local pollution prevention ordinance before the end of the year. If passed, the emission-reduction plan will go into effect in April 2001, with penalties to be levied from April 2003, when vehicles registered before September 1995 will first need to be equipped with the device. Diesel pollutants called "suspended particulate matter" are believed to cause a range of respiratory diseases. Ishihara began a drive last August to reduce air pollution from diesel vehicles in Tokyo, but it has prompted objections, particularly from the transportation industry as most large trucks run on diesel fuel. The plan will affect an estimated 650,000 vehicles registered in Tokyo and some 240,000 vehicles that pass through each day, according to the metropolitan government.