Should Ukraine, as the victim of this war, decide it's in their interests to negotiate, the US will support this as has always been the case. However, it should be noted that Russia has never been serious about diplomacy, and engaging with it should be treated with serious skepticism.
According to polls, a growing number of Ukrainians do support the prospect of starting negotiations with Russia. However, the data is clear that Putin's aspirations of holding onto Ukrainian territories are overwhelmingly rejected by the populace and that the return of Ukraine's borders should be the basis of any agreement.
The first event held by Ukraine did not resemble a peace summit in any sense of the term. The Kremlin would need to have a much firmer understanding of what the second event would entail before it can meaningfully comment on its participation.