By Nelson Bocanegra

BOGOTA (Reuters) -Colombia's government presented a tax reform bill to Congress on Monday that aims to raise 26.3 trillion pesos ($6.54 billion) in 2026 to finance next year's budget and shore up the nation's deteriorating finances.

The ambitious proposal faces an uphill battle in Congress, where President Gustavo Petro's administration has limited support, particularly with legislative and presidential elections looming next year.

"We are structuring a proposal that guarantees not only that we finance 2026, but that we are providing medium-term macroeconomic stability," Finance Minister German Avila told journalists, adding that the measures "will be of use to the next government."

The plan seeks to raise an additional 28.2 trillion pesos in 2027, with the figure rising annually to 37 trillion pesos by 2030.

The bill proposes a wide range of new levies, including a higher value-added tax (VAT) on petroleum derivatives and a new 1% tax on the first sale or export of crude oil and coal.

It also seeks to raise taxes on tobacco, alcohol, online betting, dividends and high-income earners and wealth.

In a significant shift, the reform would also impose taxes on churches, which are currently exempt, and add a surcharge on the financial sector.

The government also hopes to raise 3.5 trillion pesos next year through improved tax collection and processing by its DIAN tax agency.

Analysts are skeptical of the bill's prospects. "I see a low chance of it being approved because while a fiscal reform is being proposed, we are not seeing any proposal for better conduct in public spending," said Jackeline Pirajan, chief economist for Scotiabank in Colombia.

The proposal comes after the government suspended the country's fiscal rule in June amid falling revenues. The suspension forced the finance ministry to raise its 2025 fiscal deficit target to 7.1% of GDP, from a previous 5.1%. The deficit target for 2026 is set at 6.2%.

In response, both S&P and Moody's downgraded Colombia's debt rating.

President Petro warned in July that if Congress does not approve the reform, the government will finance its budget with more debt.

Last week, Colombia's independent Autonomous Fiscal Rule Committee (CARF) said a budget adjustment of 45 trillion pesos - far greater than the government's proposal - is needed to meet the 2026 deficit target.

($1 = 4,018.41 pesos)

(Reporting by Carlos Vargas; Writing by Brendan O'Boyle; Editing by Julia Symmes Cobb, Natalia Siniawski, Sandra Maler and Andrea Ricci)