LONDON -- It is crunch time for many of the world's biggest banks grappling with one of the tightest credit markets of recent memory.

About $120 billion of commercial paper outside the U.S. is due for renewal in the next week, including $56.5 billion of asset-backed paper, which has met the stiffest resistance from investors. Issuers need to find buyers in order to roll over these short-term funding mechanisms or pay off the loans. So banks and other issuers are pulling out all stops to lure investors back. In the meantime,...