TUNIS (Reuters) - Public finances are under strain and prices are soaring in Tunisia, presenting big economic challenges to President Kais Saied as he plans to overhaul the political system in a constitutional referendum on Monday.

Here are some of the troubles affecting the economy, which was hit particularly hard by the COVID-19 pandemic due to its reliance on tourism:

GOVERNMENT FINANCES

Strains on Tunisia's public finances have led to delays in state salaries and difficulties in paying for wheat imports.

The budget deficit is expected to widen to 9.7% of GDP this year from a previously forecast 6.7%, central bank Governor Marouan Abassi has said. This is due to a stronger dollar and sharp rises in grain and energy prices - knock-on effects of the Ukraine war that Abassi has said have generated an additional $1.6 billion of financing needs.

State finances were already stretched by one of the highest public sector wage bills in the world compared to the size of the economy, and heavy spending on imported energy and food subsidies.

A weaker Tunisian dinar has added to the pressure. The currency weakened to 3.18 dinars to the dollar in the 12 months to July 14, a 13.2% decline.

The government hopes to secure a $4 billion IMF loan in exchange for freezing public sector wages and recruitment and cutting food and energy subsidies. But the powerful UGTT labour union opposes the reforms, a significant obstacle.

DEBT SEEN MORE RISKY

The IMF said last year that Tunisia's public debt would become unsustainable unless reforms were enacted with broad support.

Tunisia’s outstanding public debt will reach nearly 114.14 billion dinars ($40 billion) by the end of 2022, accounting for 82.6% of GDP, according to the 2022 state budget, an increase from 81% in 2021.

Reflecting investor concern, spreads on Tunisian public debt - or the premium investors demand to hold it rather than ultra-safe U.S. government bonds - are now some of the highest in the world.

They have risen to over 2,800 basis points, almost three times the 1,000 level that normally sets off the warning sirens.

Along with Ukraine and El Salvador, Tunisia is on Morgan Stanley's top three list of likely defaulters.

Some $3 billion worth of Tunisian foreign currency debt is set to mature between 2024 and 2027.

Frozen out of international markets, the government hopes an IMF funding agreement would unlock wider financial support.

INFLATION CLIMBING

Tunisia's annual inflation rate has hit a series of record highs this year, touching 8.2% in June.

The government has raised petrol prices three times this year. It now costs 100 dinars to fill a typical four-door saloon compared to 93 dinars at the start of the year.