The comments come amidst heightened tensions between Powell and the president, who's repeatedly lashed out at the US central bank for raising interest rates too frequently in 2018 - while also urging policymakers to cut rates at the upcoming July meeting.
In prepared testimony, Powell says that although the economy is doing "reasonably well", since last month, "it appears that uncertainties around trade tensions and concerns about the strength of the global economy continue to weigh on the US economic outlook".
Many investors have put the odds of a rate cut this month at 100 per cent.
The Fed started cutting rates in August 2007 as the last recession swept the world.
Investors expect the Fed will cut its benchmark rate, now in a range between 2.25% and 2.5%, by a quarter percentage point at its 30-31 July meeting.
That change reflects two developments.
Powell has brushed off Trump's attacks, but in his testimony he noted that Congress has granted the central bank "an important degree of independence" to conduct policy "based on objective analysis and data". On Friday, Trump derided the Fed as the "most hard problem" facing the U.S.
Wall Street's three main indexes had retreated from last week's record closing highs after a strong June jobs report on Friday tempered expectations of a sharp rate cut this month. President Donald Trump's trade wars have magnified uncertainties.
That step eased fears that Mr. Trump would extend punitive tariffs to an additional $300 billion in Chinese goods, in the process inviting retaliation from Beijing on American exports and likely weakening both nations' economies.
"Nothing will distract us from complete focus on our job".
"Apparent progress on trade turned to greater uncertainty, and our contacts in business and agriculture reported heightened concerns over trade developments".
Little inflation pressure makes it easier for the Fed to cut short-term interest rates.
Asked Tuesday about Powell's status, White House counselor Kellyanne Conway told reporters Mr. Trump has made clear his unhappiness with the Fed's rate policies and believes "he has the power to fire Jay Powell, but he hasn't done that".
Futures markets are betting that the Fed at its 31 July meeting will cut interest rates by 25 basis points although some have seen the possibility of a larger cut.
Stocks rose and bond yields fell after Federal Reserve Chairman Jerome Powell indicated that the central is ready to cut interest rates for the first time in a decade to help shore up the economy.