(Adds details on outlook for oil revenues in 2016)
By Adriana Barrera and Ana Isabel Martinez
MEXICO CITY, Jan 15 (Reuters) - Mexico said on Thursday that tenders for the exploration and production of shale and other more expensive oil and gas deposits could happen later than planned because of the slump in oil prices, which could also hurt government spending in 2016.
The tender for Mexico's first round of contracts under an historic energy sector opening is already underway and includes several packages of fields grouped by type of basin.
Finance Minister Luis Videgaray told Mexican radio that one of the packages, first planned for 2015 and covering so-called non-conventional onshore fields, could be delayed.
Videgaray said the government might have to cut public spending in 2016 as the drop in crude prices begins to take its toll on Latin America's No. 2 economy and the reforms President Enrique Pena Nieto has banked on to revive lagging growth.
This year's public spending will not be hit, Videgaray said, thanks to an oil hedge agreed in November last year that guarantees 2015 exports at $76.40 a barrel.
Next year's spending, however, could be affected because Mexico is unwilling to borrow more or raise taxes to make up the shortfall.
"We need to start preparing ourselves for the adjustment," he said. "We're left with only one option, and that's reducing public spending."
However, slumping crude prices have not affected state-run oil company Pemex's ability to borrow. The company successfully sold a record $6 billion of debt on Thursday.
Mexico is the world's 10th biggest crude producer and oil revenue has typically made up about a third of the budget.
The price of Mexican crude mix for export was $38.48 per barrel on Tuesday, down 51 percent from the $79 dollars per barrel that lawmakers used to set the 2015 budget.
Deputy Finance Minister Fernando Aportela told Mexican lawmakers at a hearing the government would have to budget for lower oil prices in 2016 if current trends continued.
After the hearing, Aportela tried to reassure investors by saying the government would seek to avoid cuts to investment if public spending was lowered.
At the same event, fellow Deputy Finance Minister Miguel Messmacher said Mexico's 2016 budget could include tax cuts if the oil price and scale of crude production allow it.
However, Videgaray seemed to contradict this, saying that the chances of a tax cut in 2016 were now "remote." (Additional reporting by Alexandra Alper, Luis Rojas Mena and David Alire Garcia. Editing by Gabriel Stargardter, Grant McCool and Andre Grenon)