Answer:
The issue of slavery in the southern states, and the fear of a war starting with Mexico were two reasons.
Explanation:
Martin Van Buren did not want to upset either the Northerners or Southerners by admitting Texas into the Union, because then the decision would have to be made about whether to allow slavery in Texas which would throw off the balance of slave and free states. Also, Van Buren worried that Mexico would declare war if Texas was taken from them.
