WASHINGTON (AP) — Beset by hard-to-keep promises and a massive website failure, President Barack Obama is promoting his embattled health care law in the state with the highest rate of uninsured Americans, which has also been politically hostile to the signature initiative of his presidency.

Obama was traveling to Dallas on Wednesday to encourage participation in the federal insurance marketplace set up by the law. The trip to Texas comes a day after his administration tried to soothe anxious Democratic senators by reporting improvements in the troubled online enrollment system.

Meant to highlight the law's benefits, Obama's visit will also underscore the obstacles the law faces in Republican states where governors such as Texas' Rick Perry have refused to take advantage of a provision in the law that expands Medicaid to assist more of the working poor. More than 23 percent of Texas residents are uninsured.

David Simas, a White House adviser working on the law's implementation, said Obama intends to draw attention to those Republican governors who, unlike Perry, have agreed to expand Medicaid for their residents.

He said Obama will urge Texas' Republican leaders "to join conservative governors in other states, like Ohio and in Michigan and in Arizona, to put politics aside and not deny people health care out of ideology or politics."

Texas also is among the 36 states not providing their own insurance marketplaces, which means residents there must sign up through the federal website that stumbled badly upon its launch Oct. 1.

On Tuesday, Marilyn Tavenner, the head of the Centers for Medicare and Medicaid Services which is helping implement the law, told senators that repairs to the system were now permitting nearly 17,000 people to register each hour "with almost no errors."

Obama planned to visit Dallas' Temple Emanu-El, where volunteers and guides have been working with Dallas Area Interfaith to assist insurance consumers. He also plans to attend two fundraisers for the Democratic Senatorial Campaign Committee.

The president has been aggressively promoting the law in the face of numerous setbacks. In addition to the problem-plagued enrollment launch, insurers have been sending some of their customers termination notices because their policies don't meet federal requirements. The notices have put Obama and White House officials on the defensive as they attempt to explain Obama's early vow that under the new law, people who like their existing coverage would be allowed to keep it.

The Obama administration on Tuesday repeatedly refused to state a position on a mostly Republican push to write legislation that would permit insurers to reinstate canceled plans.

Secretary of Health and Human Services Kathleen Sebelius is likely to confront similar questions and more on Wednesday when she testifies before the Senate Finance Committee.

A study released Tuesday by the nonpartisan Kaiser Family Foundation estimates that the market for insurance — including the uninsured and consumers who purchase insurance individually — is 28.6 million people. The study concluded that 3 out of 5, or more than 17 million people, will be eligible for the tax credits. Texas, California and Florida have the highest numbers of residents eligible for the credits.