The ex-Presidents, Jefferson and Madison, recommended its acceptance, but the Secretary of State, John Quincy Adams, opposed this, favouring rather a separate declaration by the United States, and of this opinion was also President Monroe.

Thus arose the Monroe Doctrine announcing American opposition to the principle of "intervention," and declaring that the American continents were no longer to be regarded as open to further colonization by European nations.

The British emergency situation with France, though already quieted, caused Monroe's Message to be greeted in England with high approval.

But Canning did not so approve it for he saw clearly that the Monroe Doctrine was a challenge not merely to continental Europe, but to England as well and he set himself to thwart this threatening American policy.

Had Canning's policy been followed by later British statesmen there would have resulted a serious clash with the United States[8].
In fact the Monroe Doctrine, imposing on Europe a self-denying policy of non-colonial expansion toward the west, provided for the United States the medium, if she wished to use it, for her own expansion in territory and in influence.