NEW DELHI (Reuters) - India will fully fund its AIDS control program federally, the health minister said on Tuesday, restoring support months after it was criticized for slashing its contribution and asking individual states to fill the gap.

India's globally-lauded AIDS program has been in disarray since last year due to payment delays that worsened after Prime Minister Narendra Modi slashed the federal budget in February by a fifth and asked states to pitch in.

Several states complained of lack of clarity about how much they need to contribute and payment delays have left thousands of health workers unpaid and hampered prevention activities.

Health Minister J.P.Nadda said Modi had decided the expenses incurred in running the nationwide program will be borne by New Delhi, effectively restoring the earlier funding arrangement.

"We can't be complacent ... the government of India is very serious on this issue," Nadda said while addressing a gathering on the occasion of World AIDS Day in New Delhi.

It was not immediately clear whether the budget cut would be restored, but an official at the National AIDS Control Organization said they were in talks with the finance ministry.

The United Nations envoy for AIDS in Asia and the Pacific told Reuters in October new HIV infections in India could rise for the first time in more than a decade, as states were mismanaging the prevention program.

Government data released on Tuesday showed 86,000 new HIV infections were recorded in 2015, compared to 128,000 in 2007, but the rate of decline has slowed.

"The slowdown identified in the rate of decrease of new HIV infections in last few years is a key issue," the government said in a statement. "The current estimates highlight key challenges that will need to be addressed with urgency."

India's AIDS program has been largely successful -- estimates showed HIV prevalence during 2007-15 declined from 0.34 percent to 0.26 percent among adults, while annual HIV-related deaths declined by more than half to 67,000.

(Reporting by Aditya Kalra/Ruth Pitchford)