Obamacare v Republican plan compared
Republican politicians have campaigned on repealing President Barack Obama's healthcare reforms pretty much since they were enacted in 2010.
Now, with a governing majority, they've had to come up with a replacement plan - a task that has proved much more challenging than they may have imagined.
Here's a look at some key differences between the existing law, informally known as Obamacare, and the Better Care Reconciliation Act, which has been revised and unveiled by Republican senators.
The Senate bill reflects most of the elements that were in a bill already passed by the House of Representatives, with a few changes.
Obamacare: All Americans are required to have health insurance or pay a tax penalty.
Republican plan: The mandate is repealed under the Senate plan. The House version also repealed but with the proviso that individuals who forgo health insurance for more than 63 days must pay a 30% surcharge on their insurance premiums for a year.
Obamacare: Companies with more than 50 employees are required to offer health insurance or pay a penalty.
Republican plan: This mandate is repealed.
Obamacare: Raised Medicare taxes on the wealthy and imposed new taxes on medical devices, health insurers, drug companies, investment income, tanning salons and high-end health insurance plans.
Republican plan: The revised bill retains two key Obamacare taxes on people earning more than than $200,000 (£155,000), which helped pay for the US health scheme. The previous version had planned to eliminate the pair of taxes.
Insurance for dependents under 26
Obamacare: Requires insurers to allow children under age 26 to be covered by their parents' policies
Republican plan: Maintains this requirement.
Essential health benefits
Obamacare: Requires all insurance plans to cover certain health conditions and services, such as emergency room visits, maternity and postnatal care, cancer treatment, annual physical exams, prescription drug costs and mental health counselling.
Republican plan: Senator Ted Cruz's amendment on the latest proposal would allow insurers to offer stripped-down, low-cost healthcare plans as long as at least one complies with Obamacare rules requiring coverage for essential benefits.
Pre-existing condition coverage
Obamacare: Prohibits insurers from denying coverage or charging more to individuals who have pre-existing medical conditions.
Republican plan: Weakens protections for people with pre-existing conditions by allowing states to offer cheaper, more basic plans. Insurer groups say healthy Americans would probably purchase these "skinny" plans, destabilising the market and raising premiums on sick people, who are more inclined to buy the comprehensive plans covering essential benefits.
Obamacare: Expanded Medicaid health insurance for the poor to cover more low-income individuals.
Republican plan: Phases out Medicaid expansion to reduce federal funding on the programme over the next decade. The CBO score on the previous Senate version says that spending on Medicaid would fall 35% in 20 years. The newest Senate plan is yet to be scored.
Obamacare: Insurance companies prohibited from charging women more than men for the same health plan and must provide core services including maternity care and contraceptives.
Republican plan: Insurance companies still banned from charging women more, but states could allow insurers to drop maternity care and contraceptives from basic benefits. Also bans women from using federal tax credits to buy a plan that covers abortion.
Obamacare: Insurers can charge older Americans no more than three times the cost for younger Americans
Republican plan: Insurers can charge older Americans five times as much as younger Americans. States would also be able to set their own ratio.
Obamacare: Provided refundable tax credits for low-income individuals who purchased their insurance on government-run marketplaces and support for some out-of-pocket medical expenses.
Republican plan: Alters formula for tax credits, which will expand the benefit to more middle-class Americans but probably raise the costs for some elderly and less-affluent individuals.