Why did Britain and Mexico work against the annexation of Texas?

1845

The Republic of Texas declared independence from the Republic of Mexico on March 2, 1836. It applied for annexation to the United States the same year, but was rejected by the Secretary of State. At the time the vast majority of the Texian population favored the annexation of the Republic by the United States. The leadership of both major U.S. political parties, the Democrats and the Whigs, opposed the introduction of Texas, a vast slave-holding region, into the volatile political climate of the pro- and anti-slavery sectional controversies in Congress.