No he wasn't. He wasn't willing to go to war to fight for - or against slavery. As it turned out he ended up going to war over it anyway, but only because the southern slavocracy was bound and determined to do so.
The evidence indicates that he was very much interested in leaving everything just as it was till it became clear that he wasn't going to win easily.
And why not? If the object of the War is to get that money stream going again, the last thing he would want to do is wreck the golden goose which was paying for 3/4ths of the Federal Government, and pumping 300 million per year through New York and Boston.
But what he absolutely cannot let them do is become an independent economic rival to the Union.
As it turned out he ended up going to war over it anyway
Yes. He had two working plans to initiate belligerence with the South. If the Naval flotilla off the Coast of Charleston didn't start it, his warships heading for Ft. Pickens were going to start it anyways.
Lincoln had to have that war. That's why he insisted on keeping men in a fortress that had never been garrisoned in it's entire history, and which was utterly useless to the Union for anything other than a Causus belli.
"The plan succeeded. They attacked Sumter – it fell, and thus, did more service than it otherwise could."
Abraham Lincoln to Orville Browning.
You and I both anticipated that the cause of the country would be advanced by making the attempt to provision Ft Sumter, even if it should fail; and it is no small consolation now to feel that our anticipation is justified by the result.
Abraham Lincoln letter to Gustavus Fox.