Washington limits need a political settlement

Could Britain and the United States continue with Washington naval limits without replacing the Anglo-Japanese alliance through the Four-Power Treaty?

They could in legal theory, but the United States was unlikely to accept limits while viewing a British-Japanese combination as a threat on both coasts; failure would probably produce a short naval race and later negotiations.

The Four-Power and Washington agreements are legally separate. In practice, American planners saw Britain and Japan together as a severe two-ocean problem, with British trade influence in South America adding to the concern. Preserving the alliance without a substitute political guarantee would make the arms-limitation bargain much harder to sustain. If Washington abandoned the agreement and resumed construction, Harding's desire to reduce spending could still bring the powers back to negotiations later in the 1920s. The likely second attempt would regulate ship size more than national fleet ratios.