* Chilean peso leads Latam FX gains

* Bovespa slips as Vale weighs

* Argentine stocks up amid IMF payment report

Dec 22 (Reuters) - Latin American currencies firmed against the dollar on Wednesday, while the region's stock markets were mixed as investors assessed economic risks from the fast-spreading Omicron variant of coronavirus.

With trading volumes thinning into year-end holidays, investor focus remained on the new strain of virus that has pushed Germany, Scotland, Ireland, Portugal, the Netherlands and South Korea to reimpose lockdowns or other curbs.

The Brazilian real, the Mexican peso and Chilean peso all rose between 0.3% and 1%, in tandem with riskier currencies globally as the dollar weakened.

Brazil's Bovespa slipped 0.7%, with mining company Vale proving the biggest drag as benchmark Dalian and Singapore iron ore futures fell on concerns over COVID-19 curbs in China.

Equity markets in Colombia and Mexico edged lower, although Argentina's S&P Merval index gained 0.3% amid a report that the country will make a $1.9 billion payment to the International Monetary Fund (IMF) as it races to revamp a failed loan deal from 2018.

Argentina is seeking to roll over some $45 billion it still owes from the 2018 pact.

Meanwhile, lawmakers in Brazil's Congress approved the 2022 budget, sending it to be signed by President Jair Bolsonaro. It foresees 4.9 billion reais ($853 million) in electoral funding ahead of next year's presidential vote.

"The Brazilian Congress approved the 2022 Budget, decreasing uncertainties in the shorter-term but also confirming our expectation of a very inflexible budget," Citigroup analysts said in a note.

"In short, Congress increased some types of spending in spite of the already tough fiscal situation, decreasing the margin for adjustment in case of need of unscheduled expenses."

The Turkish lira held near recent highs after the government's measures to protect lira bank deposits from depreciation in the currency.

It backed off the day's high to trade last at 12.49 per dollar after having surged nearly 30% so far this week.

The Czech crown firmed to a six-week high against the euro after the central bank surprised markets with a larger-than-expected 100-basis-point interest rate hike to fight soaring inflation. (Reporting by Sruthi Shankar in Bengaluru Editing by Matthew Lewis)