One of Wall Street’s last remaining bears warned Thursday that the S&P 500 is approaching “mania” levels as stocks become more expensive, setting up the potential for a further surge in the near term followed by a painful pullback.

The S&P 500 topped 6,000 points for the first time, extending a strong week of gains for the blue-chip index. Wall Street’s benchmark gauge was up 0.5 per cent to briefly hit 6,000.02 just before 1pm Eastern time on Friday.

The S&P 500 breached the 6,000 mark and was poised for its biggest weekly percentage gain in a year, as Donald Trump's election victory and a possible Republican Party sweep in Congress fueled expectations for favorable business policies.