Donald Trump's announcement of immediate secondary sanctions on any country or person buying Iranian oil or petrochemicals may have a significant impact on the stock market. The move is likely to lead to increased global oil prices, as Iran is a major oil producer, and may exacerbate trade tensions between the US and other countries. Historically, Trump's aggressive stance on trade and sanctions has led to increased market volatility and negatively impacted stocks, particularly in the energy and commodities sectors. The sanctions may also lead to a decrease in international trade, which could have a ripple effect on the global economy. Furthermore, the move may lead to a decrease in the value of stocks in companies that rely heavily on Iranian oil, such as refining and petrochemical companies. Overall, the announcement is likely to lead to a bearish market sentiment, at least in the short term, as investors become increasingly cautious about the potential consequences of the sanctions.