JPMorgan Chase & Co. head Jamie Dimon said last year'svolatility in U.S. Treasuries is a “warning shot” to investors andthat the next financial crisis could be exacerbated by a shortageof the securities.

The Oct. 15 gyration, when Treasury yields fluctuated by almost0.4 percentage point, was an “unprecedented move” that would haveserious consequences in a stressed environment, Dimon, the NewYork-based bank's chairman and chief executive officer, said in aletter Wednesday to shareholders. Treasuries are supposed to beamong the most stable securities.

Dimon, 59, cited the incident as he waded into a debate aboutwhether bank regulations implemented after the 2008 financialcrisis exacerbate price declines by limiting the ability of WallStreet banks to make markets. It's just a matter of time until somepolitical, economic or market event triggers another financialcrisis, he said, without predicting one is imminent.