House Speaker John Boehner, R-Ohio, said the decision "confirms that the launch of the president's healthcare law has been an unmitigated disaster."
Other Republican leaders posted tweets deriding the decision to take healthcare.gov offline for repairs and suggesting federal officials are using the move to hide serious deficiencies in the website, The Hill reported.
"This announcement is more proof that we need to delay the law and provide basic fairness, just as Republicans have called for," Boehner said. "How can this administration tax individuals for not purchasing a product from a website that doesn't even work?"
The maintenance shutdown was announced Friday in a Department of Health and Human Services memo that said healthcare.gov would be down during "off-peak hours" Saturday and Sunday.
"The enhancements we are making will enable more simultaneous users to successfully create an account and move through the application and plan shopping process," the memo said.
"We expect that Monday, less than a week after the Marketplace opening, there will be significant improvements in the online consumer experience," it said.
HHS said an estimated 8.6 million users visited the website after open enrollment for the Affordable Care Act began Tuesday.
After experiencing widespread problems earlier in the week, the system was showing signs of improvement by Friday, The Hill said.