Clayton-Bulwer Treaty

The Clayton–Bulwer Treaty was a treaty between the United States and the United Kingdom, negotiated in 1850 by John M. Clayton and Sir Henry Lytton Bulwer, later Lord Dalling. It was negotiated in response to attempts to build the Nicaragua Canal, a canal in Nicaragua that would connect the Pacific and the Atlantic.

The United Kingdom had large and indefinite territorial claims in three regions: British Honduras (present-day Belize), the Mosquito Coast (the region along the Atlantic coast of present-day Nicaragua and Honduras) and the Bay Islands (now part of Honduras). The United States, while not making any territorial claims, held in reserve, ready for ratification, treaties with Nicaragua and Honduras which gave the United States a certain diplomatic advantage with which to balance the de facto British dominion. Agreement on these points being impossible and agreement on the canal question possible, the latter was put in the foreground.

The resulting treaty had four essential points:

The treaty was signed on April 19, 1850, and was ratified by both governments, but before the exchange of ratifications the British Prime Minister Lord Palmerston, on June 8, directed Bulwer to make a "declaration" that the British government did not understand the treaty "as applying to Her Majesty's settlement at Honduras, or its dependencies." Clayton made a counter-declaration which recited that the United States did not regard the treaty as applying to "the British settlement in Honduras commonly called British-Honduras. .. nor the small islands in the neighborhood of that settlement which may be known as its dependencies"; that the treaty's engagements did apply to all the Central American states, "with their just limits and proper dependencies" (meaning, apparently, the Mosquito Coast and the Bay Islands); and that these declarations, not being submitted to the United States Senate, could of course not affect the legal import of the treaty.

...
Wikipedia