Bib is correct. From Comprehensive Rules:
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loops
Occasionally, a game will reach a state in which a
set of actions can be repeated forever.
If a loop contains one or more optional actions
and one player controls them all, that player
chooses a number. The loop is treated as
repeating that number of times, or until another
player intervenes with his own action, whichever
comes first.
If a loop contains one or more optional actions
each controlled by different players and actions
by both are needed to continue the loop, the Free
Peoples player chooses a number. The Shadow
player then has two choices:
• He or she can choose a lower number, in which
case the loop continues that number of times,
with a final action in that loop by the Free
Peoples player.
• He or she can agree to the number chosen
by the active player, in which case the loop
continues that number of times, with a final
action in that loop by the Shadow player.
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