While I've never flown this particular combination, both DL and AS are large airlines of long standing. It is inconceivable to me that they could not interline your bag. Their code-sharing on some flights, as posted by Chuppi, reinforces that assumption further but isn't necessary for baggage interlining.

You'll also be in luck walk-wise. Both airlines use Terminal B, the pier with gates 10 through 22, at National.

(That said, confirming what #10 posted: I just got back from 11 days in Australia and Singapore, with weather ranging from below 50 in Port Arthur to the high 80s in Singapore, and including two days of business meetings - with a carry-on and a backpack.)