In a strongly worded letter to the Trump administration, Oklahoma's health commissioner recently expressed frustration that a state waiver to lower costs for Obamacare customers had not been approved as quickly as federal officials had promised.

The proposal called for a reinsurance program in which government funding pays for costly medical claims while keeping prices down for other customers. Having run out of time to make a dent in premiums, the state decided to withdraw its waiver. Health commissioner Terry Cline lamented the months that Oklahoma officials spent developing a plan, followed by six weeks of daily calls or emails with federal officials, with no results.

In Minnesota, state officials were similarly upset over the lack of federal response for their reinsurance program. The Trump administration approved it in late September, but it also reduced funding to another Minnesota program that covers 100,000 people.

Those types of complaints aren't specific to the Trump administration. Instead, they are part of a larger trend in which state officials say they are unable to make changes to healthcare programs, such as Medicaid or Obamacare, to best address the needs of their residents. State officials have said they want more flexibility not just on which healthcare programs they craft but also on how quickly federal officials approve them.

"There is a frustration that sometimes, unlike other parts of state government, Medicaid is a joint federal-state program and you have to get approval from the federal government if you're going to go out of the bounds of the federal law," said Emma Sandoe, a Medicaid researcher at Harvard University who previously worked for the Department of Health and Human Services.

The possibility of providing more state flexibility on Obamacare has been central to keeping bipartisan talks alive in the Senate and contributed to 15 governors supporting a recent bill to overhaul Obamacare, known as Graham-Cassidy. The bill would have given states block grants to set up their own healthcare systems, but it failed partly because of concerns about inadequate funding.

Still, it may be considered again next year.

"Though there were some disagreements, there is broad support for the idea of greater flexibility because that is what is going to generate solutions that actually help people," said a senior aide to one of the bill's authors, Sen. Bill Cassidy, R-La.

States have complained that filing waivers is cumbersome, involving piles of paperwork and months of work with no guarantee of approval. It can involve top officials from the Department of Health and Human Services and the Office of Management and Budget, as well as state officials and governors.

What is allowed can also vary depending on the party and priorities of an administration. For instance, the Obama administration was not willing to allow work requirements in Medicaid, while the Trump administration told governors it supports that approach.

"States try to get it in when there is an administration friendly to them. It's a political question as much as anything else," said Amy Lischko, who helped implement Massachusetts' healthcare system under Gov. Mitt Romney, after which Obamacare was modeled.

To qualify for a Medicaid waiver, states must demonstrate that their changes won't cost the federal government more and that it will "further the purpose of the Medicaid program."

Both definitions are subject to the interpretation and discretion of those running federal agencies.

"There are no stone tablets that came out of the mountain saying, 'Here are the purposes of the Medicaid program,'" said Matt Salo, executive director of the National Association of Medicaid Directors.

And the waivers have to be reapproved every few years. As of September, 33 states had 41 approved Medicaid waivers, according to the Kaiser Family Foundation. Under the Obama administration, states mostly wanted to change the way they reimbursed doctors and hospitals so that patients emerged healthier. Some states have implemented managed care programs, where private insurers are involved, and others use funds to pay for home-based care rather than nursing homes.

States can request changes to address a healthcare emergency, such as after a hurricane. Some states have a waiver that funds supportive housing or employment services for people with addiction or mental health disorders, and others target people who have HIV.

States are trying to do more. Out of cost concerns, Massachusetts is considering a waiver that would limit the number of medications covered by Medicaid and Hawaii wants to use the program to pay for helping homeless people find housing. In the past, states have pushed for housing to be covered, while others have urged coverage for air conditioners, vacuums, and other cleaning supplies that would help create healthier homes and reduce hospitalizations for patients with asthma or chronic lung diseases.

"There is a growing sense of acknowledgement that the key to helping Medicaid enrollees get healthy and keeping costs down really aren't medical services at a certain point, and that the social determinants of health can really make a difference," Salo said.

Obamacare added more waivers that states could apply for, but it included more restrictions. Former President Barack Obama initially intended for all states to expand Medicaid to low-income people, instead of specific populations as it had been before, but a Supreme Court ruling made the decision optional. As a result, 19 states haven't expanded while others have applied for waivers to implement it differently.

In Indiana, for instance, Obamacare's Medicaid expansion involves beneficiaries paying into the system and setting up a health savings account. The program typically comes at no cost to those covered, who make less than $16,642 in gross income.

"It's really important for Medicaid to be politically sustainable at the state level, and that may mean doing things differently," Salo said. "If this is important for the governor and state legislator and state taxpayers, then there is no reason why you can't make the argument that doing these things furthers the purpose of the program."

Other states have coupled the Medicaid expansion waiver with another part of Obamacare, known as the "innovation waiver." Vermont, for instance, considered a government-run healthcare system but couldn't figure out how to finance it.

J.R. Davis, a spokesman for Arkansas Gov. Asa Hutchinson, said the Trump administration has been easier to work with than the Obama administration, but the waiver is still time-consuming because it has to go through specific steps by law.

"Working to get that stuff approved has been a months-long process," Davis said. "This administration has tried to help us facilitate everything as quickly as possible, but there is still that cumbersome aspect of the paperwork and of 'dotting the I's and crossing the T's.' It just takes time."

Hutchinson, a Republican, supported Graham-Cassidy, which did not have enough Senate votes for passage. Still, it revealed support for flexibility.

"There are folks on all sides of the aisle recognizing the waiver process isn't working the way it was intended or the way folks think it should," Cassidy's senior aide said.

The bill gave states two years to implement healthcare systems, and many concluded that wouldn't be enough time. The Massachusetts healthcare overhaul, for instance, took four years to implement, and some states took more than two years to expand Medicaid under Obamacare. If Graham-Cassidy had passed, states would be nearly a year into crafting their own plans when 36 governors faced 2018 re-elections or term limits.

Still, ongoing discussions on Capitol Hill suggest the issue has traction.

"It would be nice if you could do things with a little less red tape and try programs for a shorter period of time and see whether they work," said Lischko, who is now associate professor of public health and community medicine at Tufts University School of Medicine. "States don't always have time to develop waivers and do that dance."