International lenders are making an unexpected visit to Athens to check on its resolve to implement painful austerity plans that have caused weeks of public protests and political confusion.

The team of European Union and International Monetary Fund (IMF) inspectors will visit as parliament holds a confidence vote on Tuesday night on Prime Minister George Papandreou's new cabinet, formed to stiffen the will to hammer through deeply unpopular reforms that must be passed to avoid bankruptcy.

The inspectors' trip was announced after euro zone finance ministers, meeting in Luxembourg on Sunday night, delayed approving the next 12 billion euro ($17.1 billion) tranche of aid from Greece's original bailout last year, which it needs to remain solvent for now.

Acting IMF chief John Lipsky said the Fund must be sure the reforms were on track before releasing the next tranche.

After weeks of European wrangling over how to keep Greece afloat, Lipsky told a news conference: We will all require assurances that the program is financed, and that involves assurances from our Eurogroup partners that adequate finance is available.

Greek government spokesman Ilias Mosialos said the inspectors would discuss changes at a technical level to a five-year package of spending cuts, tax hikes and public company selloffs that have touched off weeks of strikes and protests but are needed to meet the terms of a second bailout.

Greece has a sovereign debt pile of 340 billion euros, more than 30,000 euros per head of its 11.3 million population.

DEEP RECESSION

The new plan almost doubles existing belt-tightening measures that have helped drive unemployment to a record 16 percent and extended a deep recession into its third year.

Mosialos tried to dampen fears of backsliding that have unsettled international markets by saying there would be no change in the economic policy mix in the plan and only improvements in set fiscal targets would be possible.

People on the streets of Athens said they felt ashamed that the country had to ask for new loans to survive, blaming a bloated public sector, tax evasion and corrupt politicians for the country's huge debts.

I feel insulted that my country has to beg for new loans from other Europeans, said Aristoteles Michalis, 52, who owns a flower shop close to Syntagma Square where protesters have camped in front of parliament for three weeks.

The euro zone decision was intended to maintain leverage on Greek lawmakers to both support the new government and push through the new five-year package, which is a condition for a second bailout worth an estimated 120 billion euros.

We are waiting for a decision from the Greek parliament. We are calling for not just the government, but the Greek opposition to support the plan, Belgian Finance Minister Didier Reynders said ahead of a second day of meetings in Luxembourg.

CALL FOR ELECTIONS

On Sunday, opposition leader Antonis Samaras demanded Papandreou quit to pave the way for early elections and a renegotiation of the terms of Greece's current bailout, adding to market uncertainty.

Greek Finance Minister Evangelos Venizelos pledged in Luxembourg to fulfill the plan, saying Greece must urgently restore its credibility.

But he said before the trip he would try to gain approval from his euro zone counterparts to tweak the scheme.

That raised concerns the new cabinet, facing daily protests that turned violent last Wednesday, may be looking for wiggle room on the measures -- an unpalatable prospect for euro zone taxpayers who are increasingly loath to keep Athens afloat.

Worry over contagion from the Greek crisis, compounded by the delay in releasing the latest tranche, has hit European peripheral economies. The premium investors demand to hold Portuguese 10-year government bonds reached a euro lifetime high on Monday.

Ben May, EMEA economist at Capital Economics, said any delays to Greek reforms could unsettle markets.

Anything that puts an extra hoop in place that the sides have to jump through...is a worry and perhaps increases, even if it is only minutely, the chances of a default, he said.

WALKING A TIGHTROPE

Protesters planned a big rally on Tuesday ahead of the confidence motion. Workers at Greek state utility PPC launched a 48-hour strike at midnight on Sunday, which may result in rolling power outages.

With his PASOK party holding 155 of parliament's 300 seats, Papandreou's new cabinet is expected to win the confidence vote. Kicking off the debate on Sunday, he asked Greeks to get behind the austerity package and avoid a catastrophic default.

But his government is walking a fine line between trying to show its lenders it can meet tough fiscal targets and not fuelling public anger at the new reforms.

(Additional reporting by Dina Kyriakidou, Ingrid Melander, George Georgiopoulos in Athens and Jan Strupczewski in Brussels; Writing by Barry Moody; Editing by Mark Trevelyan)

International Monetary Fund