John Tyler, the US president at the time was the president that decided to independently pursue the annexation of Texas. (yr 1843)
President Andrew Jackson delayed recognizing the new republic until the last day of his presidency to avoid raising the issue during the 1836 general election.[Jackson's political caution was informed by northern concerns that Texas could potentially form several new slave states and undermine the North-South balance in Congress.
Jackson's successor, President Martin Van Buren, viewed Texas annexation as an immense political liability that would empower the anti-slavery northern Whig opposition