JOHANNESBURG (Reuters) - South Africa's rand weakened on Wednesday, with emerging markets overall on the back foot as comments by the Federal Reserve chief boosted bets on another U.S. rate hike in December. At 0630 GMT the rand was 0.42 percent weaker at 13.4200 per dollar versus a close of 13.3750 overnight in New York. In a speech on Wednesday Fed Chair Janet Yellen emphasized the need to continue with rate hikes, lifting the dollar and U.S. Treasury yields. Demand for the rand was also dampened by a political wrangle between the treasury and the state pension fund over a possible bailout for national carrier South African Airways. Bonds were also weaker, with the yield on the benchmark paper due in 2026 up 2.5 basis points at 8.565 percent. Stocks were set to open flat at 0700 GMT, with the JSE securities exchange's Top-40 futures index up 0.1 percent. (Reporting by Mfuneko Toyana; editing by John Stonestreet)