President Trump and French President Emmanuel Macron both weighed in for their countries during a crucial International Olympic Committee meeting in Switzerland on Tuesday.
Trump made his feelings known from afar, tweeting in the early-morning hours.
"Working hard to get the Olympics for the United States (L.A.)," he wrote. "Stay tuned!"
Macron took the unusual step of accompanying the Paris 2024 bid team to Lausanne, Switzerland.
Fresh off a victory over populist candidate Marine Le Pen, he addressed the IOC membership with an impassioned speech that referred to the recent election and, perhaps, Trump's nationalist policies.
"I would not be here if [the French people] had decided to prefer fear, to prefer selfishness, to refuse Europe and our values, your values," he said. "I'm here because French people decided to hope."
L.A. and Paris are locked in a tight bidding race that was expected to take an important turn.
The IOC was scheduled to vote Tuesday on a proposal to name two winners in the competition, giving the 2024 Summer Games to one city and the 2028 event to the other.
That vote was late in coming with members asking numerous questions about the scenario during an open session. At one point, IOC President Thomas Bach wondered aloud if they had their conference room rented through the next day.
Both cities began the day by giving 45-minute presentations to the IOC membership.
A final selection for 2024 — and perhaps 2028 — is scheduled for mid-September, but the IOC and the two cities could reach a negotiated agreement at an earlier date.