JOHANNESBURG (Reuters) - South Africa's rand held steady against the dollar on Friday as worries over U.S. political risk and a terror attack in Spain halted gains of risk assets. At 0906 GMT, the currency was slightly firmer, gaining 0.15 percent to 13.2400 against the greenback from its New York close. The rand was in step with Asian currencies which mostly traded flat amid concerns about whether U.S. President Donald Trump would be able to push through his economic agenda after he disbanded two business advisory councils this week. A deadly terror attack in Spanish city Barcelona, which killed 13 people, also weighed on markets. "Rand gains were halted by U.S. political risk as well as the terror attack in Spain," said RMB Global Markets analyst Isaah Mhlanga. Stocks were flat, with the JSE securities exchange's benchmark Top-40 index unchanged at 49,060 points. Government bonds were weaker, and the yield for the benchmark instrument due in 2026 was up 2.5 basis points to 8.530 percent. (Reporting by TJ Strydom; Editing by Toby Davis)