A small but expanding group of Republican senators are casting doubt on whether Republicans are moving too fast to repeal Obamacare without a replacement ready.

More than five senators expressed doubts in the last week about immediately repealing the law but leaving it intact for a few years while a replacement is created and approved. Major sticking points include adding billions of dollars to the deficit and a measure included in the repeal bill to defund Planned Parenthood.

However, Republican intransigence is likely to draw criticism from major conservative groups, with one prominent organization already saying there are "no excuses" if they fail to repeal the law now.

The Senate on Wednesday narrowly approved, 51-49, a budget resolution that will start repeal via the reconciliation process. Reconciliation ensures that a repeal bill can bypass a filibuster and be approved through a simple majority vote.

The GOP has a razor-thin margin to work with as it has a 52-48 majority in the Senate and can afford only two defections. Vice President-elect Mike Pence would be the tiebreaker.

Sens. Rand Paul, of Kentucky, John McCain of Arizona, Tom Cotton of Arkansas and Bob Corker of Tennessee have expressed doubts about repealing the law without any replacement.

Only Paul has taken action against the GOP repeal effort, voting against the budget resolution. Paul, who was re-elected in November, says he has major concerns about the hit to the deficit that repealing the law without a replacement could do.

"If Congress fails to vote on a replacement at the same time as repeal, the repealers risk assuming the blame for the continued unraveling of Obamacare," he wrote in an op-ed Tuesday for Rare Politics. "Partial repeal of Obamacare will likely win the day, but when the insurance companies come to Washington crying for a bailout, don't say that no one warned of this preventable disaster."

Other senators were worried about creating an Obamacare cliff in a few years by repealing the law without a replacement ready to go.

"Kicking the can down the road for a year is not going to make it any easier to solve," Cotton said on "Meet the Press Daily" Thursday.

Another major sticking point could be if repeal includes a provision defunding Planned Parenthood.

House Speaker Paul Ryan confirmed Thursday that the repeal legislation will include a measure defunding the women's health and abortion provider.

However, a similar provision was stripped in a 2015 repeal bill approved by Congress and vetoed by President Obama. Republican Sens. Susan Collins of Maine, Lisa Murkowski of Alabama and former Sen. Mark Kirk of Illinois worked to kill the Planned Parenthood provision in the 2015 bill.

While Murkowski's office didn't say Friday if adding the defunding provision would threaten her support for repeal, the senator was skeptical.

"She is concerned about defunding Planned Parenthood as she is a longtime supporter of the organization and has opposed broadly defunding it before," spokeswoman Jenna Mason told the Washington Examiner.

Collins also is also skeptical about linking Obamacare repeal to defunding the provider.

She told several outlets Thursday that she is not happy about Ryan's plan and has expressed concern about repealing the law without any replacement.

However, any attempt to remove the Planned Parenthood defunding from Obamacare repeal would be opposed strongly by anti-abortion groups.

It remains to be seen whether the GOP senators will vote against the repeal once it reaches the chamber.

The budget resolution will come up for a final vote before the Jan. 20 inauguration. It sets spending levels for the next decade and directs committees to draft repeal legislation by Jan. 27.

To use reconciliation, a bill must address only spending and budgetary levels. The 2015 package, which the GOP is using as a roadmap, addressed only Obamacare's taxes and mandates for getting insurance.

Crafting a repeal bill could take a while, as it took a little more than a year to develop Obamacare and then three years to implement it.

One conservative group didn't mince words when questioned on what happens if Republican leaders fail to repeal Obamacare.

"They've had all these years and all these excuses," said Nathan Nascimento, senior policy adviser for the Koch-backed Freedom Partners. "They said that getting rid of Obamacare is the first thing they can do.

"The time for excuses is over."