Legislation to ban the death penalty in Connecticut has hit a potentially fatal roadblock — the veto pen.

Gov. M. Jodi Rell took the unusual step Friday of threatening to veto the bill before it has even come to her for consideration. In a statement, Rell said she understands both sides of the contentious issue but nevertheless concluded with a terse promise: “I will veto this bill as soon as it hits my desk.”

“There are certain crimes so heinous — so fundamentally revolting to our humanity — that the death penalty is warranted,” Rell said.

Overriding Rell’s veto would take at least a two-thirds vote in both chambers of the General Assembly.  Such an override appears unlikely, given the close 19-17 vote in favor of the bill in the Senate, which passed the bill early Friday, and the 90-56 margin in the House of Representatives, which approved it last week.

“There’s no sense that an override effort would even be undertaken,” said state Sen. Andrew McDonald, Democrat of Stamford and one of the bill’s chief supporters, according to The Associated Press. “I still think the legislature made a tremendous step forward. The governor’s promise of a veto was not entirely unexpected, but it’s nonetheless unfortunate.”