Blinken left the DRC for Rwanda's capital Kigali late Wednesday afternoon, the US embassy in Kinshasa said.
Before departing, according to the US State Department, he met DRC Prime Minister Sama Lukonde and he discussed fair elections, the environment, combating corruption and "securing supply chains of critical minerals."
Blinken told reporters in Kinshasa on Tuesday evening that the United States had serious concerns about "credible reports" of Rwandan backing of the M23 -- and promised that Washington was not "turning a blind eye."
In a 131-page report to the UN Security Council seen last week by AFP, experts said Rwandan troops had intervened militarily inside the DRC since at least November.
Kinshasa blames Rwanda for backing the M23 rebel insurgency in its turbulent east, but Rwanda has repeatedly denied the claims.
The M23 is a primarily Congolese Tutsi rebel group, which has made significant advances in eastern Congo in recent months.
Relations between the DRC and Rwanda have been strained since the mass arrival in the eastern DRC of Rwandan Hutus accused of slaughtering Tutsis during the 1994 Rwanda genocide.
Relations began to thaw after DRC President Felix Tshisekedi took office in 2019 but the recent resurgence of M23 violence has reignited tensions.
Blinken's three-nation African tour, which began in South Africa on Sunday, comes shortly after an extensive African tour by Russian Foreign Minister Sergei Lavrov.