[Maédhros]

After they had marched for a great while in the unmeasured night, they came at length to the northern confines of the Guarded Realm, upon the borders of the empty waste of Araman which were mountainous and cold. There they beheld suddenly a dark figure standing high upon a rock that looked down upon the shore. Some say that it was Mandos himself, and no lesser herald of Manwë. And they heard a loud voice, solemn and terrible, that bade them stand and give ear. Then all halted and stood still, and from end to end of the hosts of the Noldor the voice was heard speaking the curse and prophecy which is called the Prophecy of the North, and the Doom of the Noldor. Much it foretold in dark words, which the Noldor understood not until the woes indeed after befell them; but all heard the curse that was uttered upon those that would not stay nor seek the doom and pardon of the Valar.

It was both a curse and a prophecy, but i think it was much more of a curse.