Question

Why did the United States initially decline to annex the Republic of Texas?

Answer 1

It applied for annexation to the United States the same year, but was rejected by the Secretary of State. ... His official motivation was to outmaneuver suspected diplomatic efforts by the British government for emancipation of slaves in Texas, which would undermine slavery in the United States.

Step-by-step explanation:

Answer 2

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. Moreover, they wished to avoid a war with Mexico, whose government refused to acknowledge the sovereignty of its rebellious northern province. With Texas's economic fortunes declining by the early 1840s, the President of the Texas Republic, Sam Houston, arranged talks with Mexico to explore the possibility of securing official recognition of independence, with the United Kingdom mediating.