At the time of the Louisiana Purchase, Texas was still part of the Spanish Empire. Immediately after the territory of the purchase was transferred to the United States, President Thomas Jefferson claimed that the purchase included lands as far as the Rio Grande. Jefferson based this claim on documents provided by the French. The Spanish government in Texas formed a plan to combat the "daring land-hunger of the infamous class of Americans." ^1 Governor Antonio Cordero planned to colonize Texas with Anglo American families. The rationale was adding more population will prevent the United States from attacking our territory.

The first military offensive occurred in 1805. A detachment of US Troops arrived in Natchitoches and claimed the area for the United States. In March 1806 Jefferson announced to Congress: "Some time since, however, we learnt that the Spanish authorities were advancing into the disputed country to occupy new posts and make new settlements." ^2 Jefferson ordered troops to disperse a Spanish detachment in the Los Adaes district. Governor Cordero ordered the local militia in Nacogdoches to reinforce the area. Commandant General Nemecio Salcedo proposed a neutral ground between Natchitoches and the Sabine River. This neutral ground would be in place until the territory dispute between the United States and Spanish Texas was resolved. ^3

In the spring of 1806, Major Thomas Freeman led an expedition along the Red River. When Commandant General Salcedo received word of this violation of Spanish territory, he issued orders for the expedition to stop it's westward movement. The expedition had traveled 600 miles up the Red River before they were confronted by a Spanish detachment. They turned back. From March to October 1806, the Spanish government of Texas reinforced their garrisonsin outposts such as the abandoned Mission San Antonio de Valera (This eventually became known as The Alamo). The troop strength by the summer of 1806 was 1,000 on the Spanish side. The United States built up their troop strength on the US border side of Texas. ^4 I don't have troop estimates for the US.

General Wilkinson, the representative of the United States, arrived at the Sabine River on October 29th, 1806. He sent a message to Governor Cordero and proposed a neutral ground agreement. This meant that the Spanish could not cross the Sabine River and the Americans would retreat to Naatchitoches and not recorss the Arroyo Hondo until the boundaries had finally been negotiated. Governor Cordero hesitated and did not accept the offer. Instead, Lieutenant Colonel Simon Herrera seized the moment and accepted the terms of the agreement. General Wilkinson and Inspector Francisco Viana signed the Neutral Ground Agreement on November 5, 1806. ^5

From 1806 to 1819, the boundaries of the Louisiana Purchase and Spanish Texas were disputed. It was the view of the United States government that the Neutral Ground Agreement of 1806 had weakened the US position. The US Secretary of State John Quincy Adams and Spanish Ambassador Luis de Onis reached an agreement to settle the dispute. The bare bones of the Adams-Onis Treaty were that Spain would keep Texas, but it would give up Florida. ^6

I believe I've at least answered the second part of your question! Maybe someone else can provide more detail on the political commentary that existed between the United States and Spanish Texas!

^1 Marks, de la Teja, Tyler, Texas: Crossroads of North America, 127.

^2 Marks, 127.

^3 Marks, 127.

^4 Marks, 128-129.

^5 Marks, 129.

^6 Marks, 145.

EDIT: Formatting