ATHENS (AFP) – Greece got no quarter from financial markets Wednesday as its borrowing costs soared and the euro sank further with investors doubting an EU-IMF deal to help Athens sort out its debts.

For the second time this week the return on Greek 10-year bonds -- a key sovereign debt instrument -- jumped above seven percent, beyond what Greece can sustain in its ongoing effort to raise billions of euros by next month. Analysis: Greek crisis coming to a head

In afternoon trade, the yield on the benchmark Greek 10-year bond was 7.096 percent, up from 6.976 percent late Tuesday but off a record high of 7.176 percent seen around midday. Bond yields usually only change incrementally.

The euro tumbled meanwhile as IMF experts began an advisory mission to help Athens enact painful budget cuts that have already sparked two general strikes while a key union warned of further action this month.

In late morning London deals, the euro slid to 1.3387 dollars from 1.3397 dollars in New York late on Tuesday.

Prime Minister George Papandreou at a cabinet meeting spurred his ministers to work harder "to implement the great changes as fast as possible," a statement from his office said.

But the union representing nearly 400,000 Greek civil servants called for strike action "between April 20 and 30" against the austerity cuts.

"Employees, pensioners and the unemployed are shouldering ... the cost of a crisis which ... capital created and is speculating on," the Adedy union said.

The deteriorating climate has also spooked Greek banks, with Bank of Greece governor George Provopoulos telling the finance ministry the country&&9;s four main lenders had applied to join a state support scheme.

National Bank, Eurobank, Alpha Bank and Piraeus Bank asked for guarantees worth 15 billion euros (20 billion dollars) under a 28-billion-euro support scheme put in place by the previous conservative administration in late 2008, semi-state agency ANA said.

A finance ministry official said the government had already decided to extend the bank support scheme by six months.

"The whole Greek economy and the banking system are under pressure so one needs to have the assurance of additional guarantees," a finance ministry source said.

The IMF mission was requested by Greece as it battles huge budget deficits and a debt mountain of nearly 300 billion euros (402 billion dollars) free credit report and score.

Athens has set itself an enormous task of slashing its budget deficit by four percentage points this year in the midst of a deepening recession.

The long-awaited EU-IMF backup loan mechanism was meant to help the country reduce its borrowing costs has so far not worked amid doubts over the exact details and contradictory reports about where Greece stood on the accord.

Analysts on Wednesday also faulted a decision by Athens to go public with plans for a US roadshow after recent bond issues met dwindling demand in Europe.

"To me, this sends the wrong signal," said Erik Nielsen, Goldman Sachs chief European economist.

He said emerging market investors had already voiced "significant concern" about Greece&&9;s debt sustainability and are generally smaller-scale investors than traditional buyers of government bonds.

"If confirmed, going for this segment of the market is a worrying sign ... Clearly some of this needs to be corrected if we are to avoid some potentially very troublesome days."

At Commerzbank, analysts said that "it has become less likely over the past few days that Greece will be able to to solve its problems on its own.

"It is becoming increasingly clear that the projected bond issue in the United States would not reduce the borrowing costs for Athens."

There is also concern that Greece&&9;s crisis measures are based on estimates that are rapidly being outpaced by the country&&9;s deepening recession.

The finance ministry has already been forced to revise its estimate on the economy&&9;s shrinkage in 2009 from 1.2 percent to 2.0 percent.

On April 22, the European Union is expected to announce that Greece&&9;s public deficit in 2009 will be higher than the 12.7 percent of gross domestic product announced by the government, local reports said.

The reports said Eurostat could put the deficit as high as 14.3 percent, mainly on the strength of huge debts owed by state hospitals.

The entire Greek state health system has debts of over six billion euros according to the government, much of it to contractors and suppliers.

Greece desperately needs tens of billions of dollars of loans at an affordable rate to be able to repay maturing debt in coming weeks and months.

Greece in loan cost spiral amid debt fears