Developing-world currencies, including the South African rand and Mexican peso, edged lower amid Trump's tariff threat.
The Bloomberg Asia Dollar Index is down 0.4% this week, heading for its largest weekly loss in six weeks, while an index for EM equities also weakened.
Despite the tariff threat, some investors remain optimistic about the longer-term trends supporting developing economies.
Markets are volatile over the uncertainty caused by tariff announcements, with investors closely monitoring US inflation data and the Federal Reserve's policy trajectory.