Obama confident of passing healthcare reform

* Obama says tough talks ahead after some Democrats rebel

* "Blue Dog" Democrats oppose public insurance option

By David Alexander

WASHINGTON (Reuters) - U.S. President Barack Obama acknowledged on Friday that tough negotiations on overhauling U.S. healthcare lie ahead after some of his own Democrats rebelled but he expressed confidence a plan will be passed.

Obama's remarks, at the end of a Group of Eight summit in Italy, came a day after a group of 40 fiscally conservative Democrats in the House of Representatives said they had "strong reservations about the process and direction" of a healthcare plan moving in the House.

Lawmakers in the Democratic-controlled Congress are working on draft proposals to revamp the U.S. healthcare system at a cost of about $1 trillion over a decade.

Healthcare reform is a key part of the Obama administration's agenda, and finding a way to pay for the cost is proving to be a major obstacle.

"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.

As Obama traveled abroad, his domestic agenda took some blows at home. In addition to the hiccup on his healthcare plan, Democrats on Thursday put off until September work on a bill to reduce greenhouse gases blamed for global warming.