A spokesman said talks between the British Medical Association and NHS Employers had been "constructive".
However, the two sides "are not able to prevent the industrial action planned".
The strike begins at 08:00 GMT across England and could affect thousands of NHS patients as junior doctors will only provide emergency care.
Earlier this week the BMA announced three spells of strike action across England, after negotiations with the government ended with no resolution.
Issues being disputed by the BMA and NHS include weekend pay.
The strike details announced are:
Acas has confirmed that talks between the BMA and NHS bosses will continue next week.
The latest round of negotiations focused on the offer made by the government in November, which would see an 11% rise in basic pay.
This would be offset by plans to cut the number of weekend hours junior doctors can claim extra 'unsocial hours' pay for.
Current rules mean that working between 7pm and 7am Monday to Friday, or any hours worked during Saturday and Sunday, attracts a premium rate of pay.
This would change with the new government proposals.
Junior doctors would receive time and a half for any hours worked between 10pm and 7am, with time and a third being paid for any hours worked between 7pm and 10pm on Saturdays or Sundays.
On-call availability allowances - ranging from 2-6% of basic pay, would also be paid to junior doctors, with additional payment for work resulting from being on call.
The government said the changes are need to create more seven-day services, but the BMA warned that they could lead to doctors being over-worked because safeguards to keep a lid on excessive hours are being weakened.
A series of protests were held across the country and 98% of BMA members who took part in the ballot backed strike action.
Talks to resolve the junior doctors dispute will "not prevent" strike action on 12 January, conciliation service Acas has said.