WASHINGTON — President Barack Obama on Saturday defended his broad health care overhaul, calling it fiscally sound and urging Congress not to squander its moment to pass reform.

Stepping up their criticism, Republicans cast the plan as a financial burden that shouldn't be rushed.

Adopting an aggressive tone, Obama spent a sixth consecutive day pushing for his top domestic priority. Growing resistance on Capitol Hill — including from conservative Democrats — has left White House officials worried they face a tougher route to legislation than they had anticipated.

"This is what the debate in Congress is all about: whether we'll keep talking and tinkering and letting this problem fester as more families and businesses go under and more Americans lose their coverage," Obama said Saturday in his weekly radio and Internet address. "Or whether we'll seize this opportunity — one we might not have again for generations — and finally pass health insurance reform this year, in 2009."

But Republicans kept up their criticism.

"The president and some Democrats insist we must rush this plan through," said Sen. Jon Kyl, R-Ariz. "Why? Because the more Americans know about it, the more they oppose it. Something this important needs to be done right, rather than done quickly."