The top bosses of JPMorgan, Morgan Stanley, Goldman Sachs and other major banks warned lawmakers Wednesday that capital hikes and other new regulations being contemplated by U.S. bank regulators will hurt lending, capital markets and the broader economy.

The industry has been waging a fierce campaign to kill the "Basel endgame" proposal, which overhauls how banks must calculate their loss-absorbing capital, and as regulators roll out fair lending and fee cap regulations, among other rules. The CEOs hope to use the hearing as an opportunity to try to convince key moderate Democratic senators that the Basel rule, which is being led by the Federal Reserve, could stifle lending, hurting small businesses and consumers.

It quickly became a battle of narratives, with many Democrats casting skepticism on the industry's complaints and accusing them of over-emphasizing the risks, while Republicans and the CEOs stressed the potential adverse impact on a range of products and services, from green lending, commodities hedging, and pension plan profits, to U.S. Treasury market liquidity.

“If enacted as drafted […], a lot of loans could become unprofitable,” CEO of the country's largest lender JPMorgan Jamie Dimon said, citing solar, wind, middle market and community lending.

The other CEOs appearing are: Bank of America's Brian Moynihan, Wells Fargo's Charles Scharf, Goldman Sachs' David Solomon, Morgan Stanley's James Gorman, State Street's Ronald O'Hanley, and BNY Mellon's Robin Vince.