A working party, including all major trading nations in the WTO, approved the final package of Saudi entry terms and agreed to pass them on for endorsement to a meeting of the body's ruling General Council on November 11.
The decision was hailed as "an historic occasion" by WTO Director-General Pascal Lamy and as "a victory for the principles and objectives of the multilateral trading system" by Saudi Commerce Minister Hashim A.Yamani.
Approval in the Council is seen as a foregone conclusion, and will clear the way - if Riyadh moves rapidly to wrap up remaining formalities - for the country to attend a major WTO ministerial meeting in Hong Kong in December as a full member.
Entry of the kingdom, which will bring WTO membership to 149, is likely to open its long-protected but growing economy to the outside world - a fact that has worried some elements in the Saudi Islamic religious establishment.
It is expected to boost foreign investment, providing funds for diversification of the largely oil-based economy, and bring new export opportunities for Saudi firms, especially in the petrochemical industry.
Yamani told the final working party session that his country had sought WTO membership "because we pride ourselves in having an open and liberal trade regime and believe in the market mechanism" as a means to growth and development.
And in the long negotiations, he said, the kingdom had made "far-reaching, very substantial and commercially meaningful concessions and commitments on goods and services" that would benefit its trading partners.
Investment has already become less cumbersome and fewer sectors are restricted to local businesses, Samba Financial Group economist John Sfakianakis said in a report on the kingdom's economic policies this week.
"Adherence to international property rights has improved and the liberalisation of the insurance market is improving," he said. Insurance was the focus of long bargaining by Saudi envoys with the European Union and the United States.
Diplomats say both powers accepted that any foreign participation in the sector would be based on the Islamic model of "co-operative insurance" when policy-holders own part of the company rather than holding individual contracts.
The talks have dragged on partly because of domestic fears that WTO free trading rules would limit Saudi Arabia's right to restrict imports of goods prohibited under Islam, including pork, alcohol or what it regards as pornography.
Further, it took years for the United States and some others to accept that Saudi Arabia was sufficiently open economically to join. On the insurance issue, EU and Saudi officials held eleventh hour talks this week to finalise an accord.
In his statement on the working party decision, Lamy - currently in New York - said both Saudi Arabia and the present WTO members with which it had negotiated bilateral pacts "have gone the extra mile" to make the entry bid succeed.
Fears among small Saudi firms at the international competition which WTO accession will bring are echoed by petrochemical producers in Europe who worry that cheap oil and gas give Saudi firms an unbeatable advantage.