To the Senate of the United States:
On the 7th day of December, 1861. I submitted to the Senate the project of a treaty between the United States and Mexico which had been proposed to me by Mr. Corwin, our minister to Mexico, and respectfully requested the advice of the Senate thereupon.
On the 25th day of February last a resolution was adopted by the Senate to the effect "that it is not advisable to negotiate a treaty that will require the United States to assume any portion of the principal or interest of the debt of Mexico, or that will require the concurrence of European powers."
This resolution having been duly communicated to me, notice thereof was immediately given by the Secretary of State to Mr. Corwin, and he was informed that he was to consider his instructions upon the subject referred to modified by this resolution and would govern his course accordingly. That dispatch failed to reach Mr. Corwin, by reason of the disturbed condition of Mexico, until a very recent date, Mr. Corwin being without instructions, or thus practically left without instructions, to negotiate further with Mexico.
In view of the very important events occurring there, he has thought that the interests of the United States would be promoted by the conclusion of two treaties which should provide for a loan to that Republic. He has therefore signed such treaties, and they having been duly ratified by the Government of Mexico he has transmitted them to me for my consideration. The action of the Senate is of course conclusive against an acceptance of the treaties on my part. I have, nevertheless, thought it just to our excellent minister in Mexico and respectful to the Government of that Republic to lay the treaties before the Senate, together with the correspondence which has occurred in relation to them. In performing this duty I have only to add that the importance of the subject thus submitted to the Senate can not be overestimated, and I shall cheerfully receive and consider with the highest respect any further advice the Senate may think proper to give upon the subject.
ABRAHAM LINCOLN.
Abraham Lincoln, Message to the Senate on a Treaty with Mexico Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/202292