DUBAI, Feb 21 (Reuters) - Saudi Arabia has sent a request for proposals (RFP) to banks for a planned U.S. dollar sukuk, or Islamic bond, two sources familiar with the matter said on Tuesday.

The debt sale would be Saudi's second international bond offering, after the sovereign issued a debut $17.5 billion bond in October last year in what was the largest bond ever sold across emerging markets.

The government approached lenders which had worked on Saudi's first issuance, one of the sources said.

Saudi's first bond was arranged by Citi C.N , HSBC HSBCUK.UL , JP Morgan JPM.N as global coordinators, with Bank of China 601988.SS , BNP Paribas BNPP.PA , Deutsche DBKGn.DE , Goldman Sachs GSGSC.UL , Morgan Stanley MS.N , MUFG MTFMSI.UL , and NCB Capital also involved.

Saudi Arabia is also expected to issue a conventional bond later this year, another source said separately.

The kingdom's bond plans are part of its push towards a more diversified economy that is less reliant on oil exports.

The RFP was issued at a busy time in the Gulf debt markets, with other countries such as Bahrain and Oman planning to raise funds internationally to offset the impact of lower global oil prices.

Bahrain launched a tap of its $1 billion 2028 bond on Tuesday, while Oman is expected to announce the launch of a new bond this week.

(Reporting by Celine Aswad and Sudip Roy; writing by Davide Barbuscia; editing by Louise Heavens and Richard Lough) ((Davide.Barbuscia@thomsonreuters.com;))