Here are two relevant passages:
Third Nephi 16:
 Behold, because of their belief in me, saith the Father, and because of the unbelief of you, O house of Israel, in the latter day shall the truth come unto the Gentiles, that the fulness of these things shall be made known unto them.And Third Nephi 21:
 But wo, saith the Father, unto the unbelieving of the Gentiles -- for notwithstanding they have come forth upon the face of this land, and have scattered my people who are of the house of Israel; and my people who are of the house of Israel have been cast out from among them, and have been trodden under feet by them;
 And because of the mercies of the Father unto the Gentiles, and also the judgments of the Father upon my people who are of the house of Israel, verily, verily, I say unto you, that after all this, and I have caused my people who are of the house of Israel to be smitten, and to be afflicted, and to be slain, and to be cast out from among them, and to become hated by them, and to become a hiss and a byword among them --
 And thus commandeth the Father that I should say unto you: At that day when the Gentiles shall sin against my gospel, and shall reject the fulness of my gospel, and shall be lifted up in the pride of their hearts above all nations, and above all the people of the whole earth, and shall be filled with all manner of lyings, and of deceits, and of mischiefs, and all manner of hypocrisy, and murders, and priestcrafts, and whoredoms, and of secret abominations; and if they shall do all those things, and shall reject the fulness of my gospel, behold, saith the Father, I will bring the fulness of my gospel from among them.
 And then will I remember my covenant which I have made unto my people, O house of Israel, and I will bring my gospel unto them.
 And I will show unto thee, O house of Israel, that the Gentiles shall not have power over you; but I will remember my covenant unto you, O house of Israel, and ye shall come unto the knowledge of the fulness of my gospel.
 But if the Gentiles will repent and return unto me, saith the Father, behold they shall be numbered among my people, O house of Israel.
 And I will not suffer my people, who are of the house of Israel, to go through among them, and tread them down, saith the Father.
 But if they will not turn unto me, and hearken unto my voice, I will suffer them, yea, I will suffer my people, O house of Israel, that they shall go through among them, and shall tread them down, and they shall be as salt that hath lost its savor, which is thenceforth good for nothing but to be cast out, and to be trodden under foot of my people, O house of Israel.
 Therefore it shall come to pass that whosoever will not believe in my words, who am Jesus Christ, which the Father shall cause him to bring forth unto the Gentiles, and shall give unto him power that he shall bring them forth unto the Gentiles, (it shall be done even as Moses said) they shall be cut off from among my people who are of the covenant.These are amazing days, days that ancient prophets on this law saw in vision. There is no security in wealth and possessions and pleasure, only in living the Gospel of Jesus Christ. The remnants of the House of Israel will play a key role in building the New Jerusalem and preparing for the return of the Savior, but before then, some of them may well prove to be tools of the Lord in bringing vengeance to a wicked and corrupt nation. And it's not hard to see how Book of Mormon prophecy on this matter could be fulfilled. Food for thought. Speaking of which, how's your food storage doing? Got food?
 And my people who are a remnant of Jacob shall be among the Gentiles, yea, in the midst of them as a lion among the beasts of the forest, as a young lion among the flocks of sheep, who, if he go through both treadeth down and teareth in pieces, and none can deliver.
 Their hand shall be lifted up upon their adversaries, and all their enemies shall be cut off.
 Yea, wo be unto the Gentiles except they repent; for it shall come to pass in that day, saith the Father, that I will cut off thy horses out of the midst of thee, and I will destroy thy chariots;
 And I will cut off the cities of thy land, and throw down all thy strongholds;
 And I will cut off witchcrafts out of thy land, and thou shalt have no more soothsayers;
 Thy graven images I will also cut off, and thy standing images out of the midst of thee, and thou shalt no more worship the works of thy hands;
 And I will pluck up thy groves out of the midst of thee; so will I destroy thy cities.
 And it shall come to pass that all lyings, and deceivings, and envyings, and strifes, and priestcrafts, and whoredoms, shall be done away.
 For it shall come to pass, saith the Father, that at that day whosoever will not repent and come unto my Beloved Son, them will I cut off from among my people, O house of Israel;
 And I will execute vengeance and fury upon them, even as upon the heathen, such as they have not heard.
 But if they will repent and hearken unto my words, and harden not their hearts, I will establish my church among them, and they shall come in unto the covenant and be numbered among this the remnant of Jacob, unto whom I have given this land for their inheritance;
 And they shall assist my people, the remnant of Jacob, and also as many of the house of Israel as shall come, that they may build a city, which shall be called the New Jerusalem.
 And then shall they assist my people that they may be gathered in, who are scattered upon all the face of the land, in unto the New Jerusalem.