The president announced the sanctions relief in May, ahead of an unannounced visit with Syrian leader Ahmed al-Sharaa.
Investors interpreted Trump's comments to mean Nippon Steel had received his approval for its takeover.
Opposition leaders have argued the detention of politician Juan Pablo Guanipa and others is meant to stifle dissent.
Kabila, accused of ‘treason’ and ‘war crimes’, denies government accusations of links to M23 rebel group.