As the Fed tries to stay firmly out of the limelight, markets are buckling up for another Trump tirade

Whether or not they'd like to admit it, there will be an elephant in the room when the U.S. central bank's Federal Open Market Committee (FOMC) meets this week.

The Jerome Powell-led group have said time and again their decision-making process—namely what to do with America's interest rate—is based on economic data and anecdotal evidence from business owners and employees. Politics never comes into it , they have specified.

And yet President Donald Trump seems determined to insert himself into the conversation —whether it's pressuring the FOMC to hold or lower rates, or saying he should be the one making the final call.

With Powell widely expected to announce a hold of rates at 4.25% to 4.5% following the meeting this week, markets are already bracing for a tirade from President Trump which may inject even more volatility into the already turbulent outlook.

Trump's potential intervention is unorthodox in the historic relationship between central bank and government , where there is usually a clear line between church and state.

The reasoning for the federally-mandated divide is clear : The base rate, which impacts everything from employment to foreign investments to the bond market, cannot be used as a pawn in the game of politics .

The role of the FOMC is to ensure the base rate is used to ensure two things: Maximum employment and an inflation rate of 2%, steadying the economy over the long term.

The regional bank presidents and economists who make up the FOMC have a complicated tapestry to unpick when determining their decision.

One of the issues raised will of course be the White House's tariff policy—which has been mentioned by the FOMC before not as commentary on the policy, but on their potentially inflationary effects.

However the picture is muddied by the fact the rates announced on 'Liberation Day' were higher than analysts feared, but subsequently delayed by the Oval Office pending deals with key trading partners which are yet to be confirmed.

Uncertainty is firmly rooted into the outlook, wrote Deutsche Bank's Jim Reid in a note this morning seen by Fortune .

"Our U.S. economists expect the FOMC to keep rates steady and avoid explicit forward guidance about the policy path ahead," Reid said. "They continue to see the next rate cut coming in December and while risks are tilted towards earlier easing, in their view this would require a clear weakening of the labour market."

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