UPDATE 3-Obama seeks to regain intiative on healthcare

(For a take a look on healthcare, click on [ID:nN07323916])

* Obama says debate, disagreements ahead on health issues

* Leading Democrat says health overhaul on track in Senate

* Health insurers discuss $100 billion savings (Adds Representative Rangel after White House meeting)

By Steve Holland and David Alexander

WASHINGTON, July 13 (Reuters) - A combative President Barack Obama on Monday sought to regain the initiative on overhauling the U.S. healthcare system after legislation slowed down in the Congress while he was abroad last week.

Obama, just back from a week-long trip to Europe and Africa, used a Rose Garden ceremony to make his case for the healthcare revamp and to tell his critics they should not write him off too soon on the subject.

"I just want to put everybody on notice, because there was a lot of chatter during the week that I was gone: We are going to get this done. Inaction is not an option."

"For those naysayers and cynics who think that this is not going to happen, don't bet against us. We are going to make this thing happen," he said.

Several lawmakers on Sunday talk shows said healthcare, Obama's number one priority, could not be finished by August amid controversy over how to pay for its $1 trillion cost over 10 years. House of Representatives Democrats set off a furor on Friday with a plan to tax the wealthy to pay for healthcare.

Senate Majority Leader Harry Reid said on Monday the goal was unchanged. "We'd like to see these bills on the floor in July. And we hope our Republican colleagues will work with us to achieve that goal," he said on the Senate floor.

Earlier in the day, Obama predicted more debate in the days ahead as panels in both chambers consider various versions of the healthcare plan but said he would be successful in fulfilling his campaign pledge.

"Even though we are close, I've got no illusions that it's going to be easy to get over the finish line. There are going to be more debates and more disagreements before all is said and done, but healthcare reform must be done," Obama said.

Obama was also scheduled to travel on Tuesday to Warren, Michigan, a state where closed factories and the highest unemployment rate in the country have left many without private health insurance and struggling to pay medical bills.

After top Democrats in both chambers went to the White House for a meeting with Obama, Senate Finance Committee Chairman Max Baucus told reporters: "There was the strongest commitment yet ... from everyone there that we are all going to work together to get this passed."

Baucus, whose panel is crafting a major portion of the bill including how to pay for the overhaul, added, "I got the sense that the urgency barometer is going up."