Two Presidents one citation? Found Andrew Jackson and, one suspects, he was being misquoted as Monroe elsewhere. Not in a treaty but a 'personal message' to the Creek Nation treaty hold-outs. Delivered March 1829 by the local Indian Agent. Not sure of the audience/forum:

“INDIAN TALK.
From the President of the United States, to the Creek Indians, through Colonel Crowell*.
… Friends and Brothers. listen:—Where you now are, you and my white children are too near to each other to live in harmony and peace. Your game is destroyed, and many of your people will not work and till the earth. Beyond the great river Mississippi, where a part of your nation has gone, your father has provided a country large enough for all of you, and he advises you to remove to it. There your white brothers will not trouble you; they will have no claim to the land, and you can live upon it, you and all your children, as long as the grass grows or the water runs, in peace and plenty. It will be yours for ever. For the improvements in the country where you now live, and for all the stock which you cannot take with you, your father will pay you a fair price.”
[Documents and Proceedings Relating to the Formation and Progress of a Board in the City of New York for the Emigration, Preservation, and Improvement, of the Aborigines of America, 22 July 1829]

Joseph John Crowell (1780 – 1846)
“In the election of 1818, he became the first member of the House of Representatives from the new state of Alabama. When he retired after one term in 1821, President James Monroe appointed him the United States Indian agent to the Creek Indians.” [wiki]

Col. Crowell was still agent to the Creek Nation when Presidnt Andrew Jackson took office in March 1829.