WASHINGTON: President Barack Obama's core legislative agenda -- overhauling healthcare and addressing climate change -- has hit some stumbling blocks in the U.S. Congress.

Here are some questions and answers about the issues.

WHAT'S GOING ON WITH THE HEALTHCARE OVERHAUL?

Dozens of fiscally conservative Democrats, worried about the estimated $1 trillion cost, are demanding some big changes in a healthcare plan working its way through the House of Representatives. That likely will delay the official roll-out of a version of the legislation on Friday.

Healthcare is Obama's top legislative priority and he wants to sign a bill by the end of October to make healthcare more affordable for millions of Americans who are either having trouble paying for health insurance or doing without.

But the cost of the program -- and how to pay for it -- may force Obama to forswear his campaign pledge not to raise taxes on anyone making less than $250,000 a year.

IS THE OVERHAUL IN TROUBLE?

In the end, probably not. Most major legislation on Capitol Hill moves in fits and starts. Democrats who control the U.S. Congress ultimately want to come to an agreement and they are well aware of how Bill and Hillary Clinton's healthcare effort collapsed in acrimony in 1993.

"There are going to be some tough negotiations in the days and weeks to come but I'm confident that we're going to get it done," Obama said on Friday at the end of a Group of Eight summit in Italy. He said Americans were closer to "significant reform than at any time in recent history."