South Africa's rand firmed early on Thursday against a weaker U.S. dollar, but failed to reclaim significant gains from the previous day's budget speech.

At 0804 GMT, the rand traded at 18.8500 against the dollar , about 0.4% stronger than its previous close.

The dollar index was trading down about 0.32% as traders awaited a slew of business activity surveys from major economies.

The rand initially jumped on Wednesday after the annual budget speech, in which the finance minister said the government would tap 150 billion rand ($7.99 billion) from a central bank-administered contingency account in order to limit borrowing. But most of the gains had been reversed by the end of the day.

"What rallies have followed should be classified more as relief rallies than they should be considered proof that this was a well-received budget," said ETM Analytics in a research note.

The Treasury's withdrawal from the Gold and Foreign Exchange Contingency Reserve Account (GFECRA) is a quick fix but will not help address the many problems plaguing South Africa's economy, which barely grew in the last decade, said ETM.

On the stock market, the Top-40 index was up about 1.1% in early trade. South Africa's benchmark 2030 government bond was slightly weaker in early deals, with the yield up 1 basis points to 10.035%. (Reporting by Nellie Peyton; Editing by Ros Russell)