JOHANNESBURG (Reuters) - South Africa's rand rose to its firmest in nearly one month on Monday while government bonds also strengthened after S&P Global Ratings affirmed the country's investment-grade credit status on Friday.

S&P left its BBB- rating on Africa's most industrialised economy but warned that its negative outlook reflected the potential adverse consequences of low GDP growth.

By 1515 GMT the rand <ZAR=D3> had gained 1.25 percent to 14.9105 per dollar, its firmest since May 12, breaking through a number of key technical milestones as the greenback floundered with bets of a rate hike by the U.S. Federal Reserve receding.

"The rand has broken below its 50-day moving average at 15.00, which from a technical perspective is quite an important move. If it can close below that it would be rand positive," market analyst at ETM Analytics Ricardo Da Camara said.

The rand was also firmer against the British pound <GBPZAR=> and the euro <EURZAR=>, gaining 1.7 percent and 1.1 percent against the currencies respectively.

Government bonds also firmed, with the yield on the benchmark paper due in 2026 <ZAR186=> falling 16 basis points to 9.04 percent, its firmest since May 9. South Africa's dollar-denominated bonds also firmed.

The rand added to gains achieved on Friday after weak employment figures from the United States data quashed expectations for a near-term U.S. interest rate hike, boosting appetite towards riskier emerging market assets.

Traders said the rand was in line to stretch the recent gains ahead of a speech by Federal Reserve chairwoman Janet Yellen later in the session.

"After Friday's nonfarm payrolls report investors are going to put a lot of weight on what Janet Yellen says today," Da Camara said.

On the bourse South African equities fell, led by petrochemicals group Sasol <SOLJ.J>, which slid over 12 percent after it flagged lower annual earnings and said costs would rise on a major U.S. project.

The benchmark Top-40 index <.JTOPI> fell 0.5 percent to 47,822 while the wider All-share index <.JALSH> also ended 0.5 percent lower at 53,991, reversing two straight sessions of gains.

Sasol's shares closed 11 percent lower at 433 rand. The company raised its forecast for the cost of its U.S. ethane cracker by 26 percent to as much as $11 billion due to construction delays.

Telkom SA <TKGJ.J>, South Africa's biggest landline provider, leapt 8 percent to 65 rand after reporting a 15.5 percent jump in annual earnings and announcing the end of its cost-cutting strategy.

Overall, around 229 million shares changed hands, compared with last year's daily average of 280 million, according to preliminary bourse data.

(Reporting by Mfuneko Toyana and Ed Stoddard; Editing by James Macharia)