。
Supplies will soon be insufficient.
Literal
Supply [subject-が] soon be-insufficient probably (polite).
Notice the が rather than は on 補給. が presents 補給 as new or focused information ('[it is] supply that will soon...'), while は would topicalize it as already-established context ('as for supply...'). In announcements and reports both readings are natural, but the choice subtly signals what the speaker expects the listener to already know about the situation.