A flat naval budget can cut a fleet without an explicit vote

How likely is Congress to cut the US Navy during a delay in the Washington treaty process?

Very likely in real terms, because flat funding, inflation, and operating demands can stop construction even without a formal budget cut.

Legislators do not need to reduce a nominal appropriation to shrink a navy's real program. Inflation, operating costs, and unplanned deployments can absorb money intended for construction. Senator Tillman might block an overt reduction, but he could not necessarily secure every annual increase required to finish an ambitious battle fleet. Ships might consequently be delayed, canceled, or sold abroad even while the headline budget appeared unchanged.