* Reserve Bank March business cycle indicator due at 0700 GMT

* First quarter GDP due at 0930 GMT

JOHANNESBURG, May 27 (Reuters) - South Africa's rand weakened slightly against the dollar early on Tuesday and looked vulnerable ahead of economic growth data that is likely to validate the central bank's decision to keep interest rates unchanged last week.

The rand ZAR=D3 traded at 10.3650 to the dollar at 0630 GMT, 0.2 percent weaker than its close in New York on Monday.

The local currency could weaken out of Monday's range if economic growth data underperforms market expectations.

Investors will be focused on first quarter GDP numbers due at 0930 GMT. The consensus is for growth to have contracted to 0.1 percent quarter-on-quarter. ZAGDP=ECI

The number will validate Governor Gill Marcus' decision to hold interest rates at 5.5 percent last week due to concerns about faltering growth.

In an otherwise uneventful monetary policy statement, the bank slashed its 2014 growth expectations to 2.1 percent from 2.6 percent, adding that GDP in the first three months of this year was expected to be the lowest quarterly expansion since a 2009 recession. ZAREPO=ECI

Government bonds mimicked the rand's slight weakness on Tuesday morning as traders also waited for the weekly sale of the government's 2030 ZAR2030= , 2037 ZAR2037= and 2048

ZAR2048= debt. Results are due after auction closes at 0900 GMT.

The 2015 yield ZAR157= climbed 2 basis points to 6.65 percent and 4.5 basis points to 8.17 percent on the 2026 note

ZAR186= .

(Reporting by Xola Potelwa; Editing by Ed Cropley)

((xola.potelwa@thomsonreuters.com)(+27 11 775 3098)(Reuters Messaging: xola.potelwa.thomsonreuters.com@reuters.net))

Keywords: MARKETS SAFRICA/CURRENCY