BUENOS AIRES, May 2 (Reuters) - Argentina's nuclear energy ambitions are coming under pressure from a tough austerity package and cost-cutting drive by libertarian President Javier Milei, the head of the National Atomic Energy Commission (CNEA) told Reuters.

The squeeze on the budget of CNEA, which oversees research and development of nuclear energy in Argentina, has stalled construction work on the cutting-edge CAREM small modular reactor and other projects, Adriana Serquis said.

"The budget problem is serious not only for large projects but for the entire operation of the institution," Serquis said in an interview at the CNEA offices.

"Without a concrete plan it is very difficult to know how to prevent these works from suffering further damage and ending up being inefficient in their investment."

The Energy Ministry did not respond to a request for comment.

The CNEA said in a statement its budget had been held at 2023 levels of around 100 billion pesos ($114 million), despite annual inflation nearing 300%, meaning the amount was only enough to cover expenses until this month or next. Transfer of part of the expected budget had also been delayed, it added.

Some suppliers and contractors had been forced to halt work on the CAREM construction and other projects and were not able to pay workers, Serquis said.

Milei's government, which took over in December amid a major economic crisis and deep fiscal deficit under the last government, has pledged to cut costs and rebalance the state's finances. He also wants to privatize some state entities.

His cost cutting measures have sparked protests by worker unions and recently by teachers and students at public universities, who are also feeling a major budget squeeze.

Small modular reactors (SMR) are used to produce electrical energy through nuclear fission and are expected to help in the transition process towards clean energy. Currently, other countries building them include China, Japan and Russia.

Work on the Argentina SMR, financed entirely by the state, began in 2014 and is expected to be completed by 2028. ($1 = 876.5000 Argentine pesos) (Reporting by Candelaria Grimberg and Horacio Soria; Editing by Nicolás Misculin, Alexandra Hudson)