How to assign result of async pipe to variable without *ngIf in Angular 6

Is it possible to assign (areShipsExpanded$ | async) to variable without *ngIf? Because in case that this is flag true/false when I have: *ngIf="(areShipsExpanded$ | async) as flag" then button is not displaying in case of false.

And I would like something like this:

<button *let="(areShipsExpanded$ | async) as flag"
(click)="expandAllShips(flag)">{{(flag ? "Collapse" : "Expand"}}
</button>

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