The pledge was made by Children's Minister Aileen Campbell as the Conservatives said the SNP's plans were in chaos.
She said the legal delay was to allow resolution of "issues around the margin" but she stressed both the Scottish Government and local authority body Cosla expected the childcare to be in place for two-year-olds whose parents do not have a job from August.
Opposition politicians have already begun claiming the delay in bringing forth the legal duty showed the Government is in "disarray'' on the issue of childcare.
Ms Campbell told the Scottish Parliament's Education Committee that ministers had been working hard with Cosla to "ensure that our ambitious timescale" for the new childcare policy is met.
She added: "Every local authority has plans in place and is in a very strong position to deliver from August."
Scottish Conservatives spokeswoman Liz Smith MSP said: "The performance from the minister on this crucial subject was a farce.
"We still have no guarantee that all eligible two-year-olds will receive a place from August."
l Ms Campbell is expecting her second child, becoming the first member of the Scottish Government to have a baby while in office.