DUBAI  - Global equity index compiler S&P Dow Jones Indices will upgrade Saudi Arabia's bourse to emerging market status from a stand-alone market next year, becoming the latest in a series of index firms to promote Riyadh.

S&P Dow Jones will add major Saudi stocks to its global indexes with a 50 percent weighting in March 2019 and raise their weightings to 100 percent in September, the company said in a statement late on Tuesday.

The company had been considering a Saudi upgrade for several years but decided against one last year because of limited market access for foreign investors.

It said on Tuesday that it was acting in response to reforms of Riyadh's market structure supporting foreign investment as well as a strong, positive consensus among members of the investment community.

FTSE Russell decided in March this year to upgrade Saudi Arabia to an emerging market in 2019, which fund managers expect will attract about $5 billion of "passive", index-linked money to the bourse. MSCI made a similar decision in June; an MSCI upgrade could attract around $10 billion of passive funds.

S&P Dow Jones previously estimated Saudi Arabia could have a 2.57 percent weighting in its emerging benchmark index. It did not say how much money was linked to that index, but fund managers say it is considerably less than the amounts benchmarked to the FTSE Russell and MSCI indexes.

(Reporting by Andrew Torchia Editing by Andrew Heavens) ((andrew.torchia@thomsonreuters.com; +9715 6681 7277; Reuters Messaging: andrew.torchia.thomsonreuters.com@reuters.net))