When Secretary of State Upshur accelerated the secret negotiations, Mexican diplomats learned that talks were taking place between the United States and Texas. The Mexican Minister of the United States, Juan Almonte, confronted Upshur with these reports and warned him that if Congress sanctioned an annexation treaty, Mexico would sever diplomatic relations and immediately declare war.  Secretary Upshur dodged the accusations and advanced the negotiations.  Along with Texas diplomats, Upshur secretly complained in favor of U.S. senators` support for the annexation and provided lawmakers with compelling arguments that associate the acquisition of Texas with national security and internal peace. Early in 1844, Upshur was able to assure Texan officials that 40 of the 52 members of the Senate were forced to ratify the Tyler-Texas Treaty, more than the two-thirds majority required to pass it.  Tyler remained silent in his annual address to Congress in December 1843 on the secret treaty, so as not to harm relations with prudent Texan diplomats.  Tyler did everything he could to keep the negotiations secret, and did not publicly refer to his government`s proactive research in Texas.  Andrew J. Donelson brought the proposal to Texas and insisted that it be adopted immediately. The United States government had good reason to ask for help for both England and France, in the hope that Texas might be encouraged to refuse annexation and remain independent, to have pushed Mexico to accept a peace treaty. Anson Jones, President of Texas, approved the preliminary work of a treaty with Mexico, in which that country agreed to recognize Texas` independence provided That Texas was not annexed to the United States. Jones presented both to the Congress of the Republic (how is it possible if Congress was never convened after his election?) and to the People of Texas (Which people and when?) who accepted the terms of the annexation by the 1845 Convention (only 57 delegates present and only 13 of them from Texas).
This action put an end to all diplomatic activities of the Republic, although some time elapsed before the return of the various foreign representatives from Texas. The annexation of Texas to the United States became, after the Louisiana Purchase in 1803, a subject of political and diplomatic conversation and became a matter of international interest between 1836 and 1845, when Texas was a republic. In September 1836, Texas voted overwhelmingly in favour of annexation, but when the Texas minister of Washington, D.C., in August 1837, proposed the annexation of the Martin Van Buren government, he was told that the proposal could not be maintained. Constitutional scruples and fear of war with Mexico were the reasons for the rejection, but the anti-slavery atmosphere in the United States undoubtedly influenced Van Buren and continued to be the main obstacle to annexation. Texas withdrew the annexation offer in 1838; President Mirabeau B. Lamar (1838-1841) refused the annexation and did not rest the question. At the beginning of his second term (1841-44), Sam Houston tried unsuccessfully to attract the interest of the United States. A constitutional convention elected by the people met in Austin in July 1845 to discuss this proposed annexation and a proposed peace treaty with Mexico, which would end the state of war between the two nations if Texas remained an independent country. Politically, the Brown Amendment was designed to portray the Southern Whigs as “even more fervent advocates of slavery and the South than the Southern Democrats.”  The bill also served to distinguish them from their colleagues in northern Whig, who characterized the controversy, as Calhoun, strictly for anti-slavery.  While almost all Northern Democrats despised Brown`s amendment, Democrats quickly co-opted the law and provided the votes needed to give the votes needed to Tyler`s joint resolution by 118-101 votes.  The Southern Democrats supported the bill almost unanimously (59-1), while the Northern Democrats voted strongly (50-30).