Answer:
He insisted that his only goal was to save the union because he knew that if they chose to secede, the union could be lost.
Step-by-step explanation:
The Border states are the ones that are on the border between North and South during the Civil War - such as Maryland, Delaware, Kentucky, and Missouri -, they remained loyal to the Union even though slavery was legal within their borders.
President Abraham Lincoln knew that while the economy of those states was not tied to slavery most of the population of them did not agree politically with Lincoln. He did not want to offend them by being too aggressive by being opposed to slavery. He eventually kept the border states within the Union.