pledged

Athens (CNN) -- Exit polls pointed to a neck-and-neck finish in Greece's parliamentary elections Sunday between a party pledged to continue with an unpopular bailout program and one vowing to tear it up.

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Is "pledged" there used as an adjective? Thank you.

Don't you think it modifies "party"? What could it be other than an adjective?

cyberpedant said:

Don't you think it modifies "party"? What could it be other than an adjective?

I was thinking whether it is the past participle of "pledge" and wondering why the present participle is not used.