WASHINGTON (REUTERS) - US stocks advanced on Friday, driven by Apple, as a sense of calm prevailed over Wall Street in a week that was dominated by political uncertainty surrounding Donald Trump's presidency.

Still, the indexes are on track for their worst weekly declines since mid-April after Mr Trump unexpectedly fired FBI Director James Comey. Reports later alleged Trump had asked Comey to end an investigation into former national security adviser Michael Flynn's ties with Russia.

Investors fear that the political uproar in Washington could hinder Mr Trump from pursuing his promise of fiscal stimulus, a key driver for Wall Street's record-setting run.

"The market is looking to stabilize as no new political news hit this morning headlines, suggesting that investors are willing to play out the political turmoil without pushing the panic switch," Peter Cardillo, chief market economist at First Standard Financial wrote in a note.

Apple was up 0.6 per cent and was the top stock on all three major Wall Street indexes. Shares of the most valuable US-listed company have been recovering after their biggest one-day drop in more than a year on Wednesday.

At 9:39 a.m. ET (9:39 Singapore time), the Dow Jones Industrial Average was up 53.44 points, or 0.26 per cent, at 20,716.46, the S&P 500 was up 9.23 points, or 0.39 per cent, at 2,374.95 and the Nasdaq Composite was up 32.44 points, or 0.54 per cent, at 6,087.57.

Nine of the 11 major S&P 500 sectors were higher. Technology was in the lead with a 0.58 per cent increase, followed by a 0.51 per cent rise in financials.

The S&P 500 index showed eight new 52-week highs and five new lows, while the Nasdaq recorded 31 new highs and 20 new lows.