The rocket, which will carry Aist-2D, Mikhailo Lomonosov and SamSat-218 research satellites, will begin its ascent on 02:01 GMT.
"On way or another, the president will, of course, watch the launch, but I cannot say in what manner this will be done," Peskov told reporters.
The Vostochny Cosmodrome has been under construction since 2012 and is expected to reduce Russia's dependency on the Baikonur space center in Kazakhstan. Baikonur is on lease to Russia until 2050. The spaceport was set to be completed by late 2015, with the first launch scheduled for December 2015. The launch was later postponed due to construction delays.