* Juncker says Greece won't go bust, no need for EU help
* ECB's Nowotny sees no risk of euro breakup over Greece
* Greek bond spread narrows after Soros sees no default
By Boris Groendahl and Sarah Marsh
VIENNA/BONN, Germany, Dec 10 (Reuters) - Greece will not need financial help from peers in Europe and there is no danger of its budget woes leading to a break-up of the euro zone, European policymakers said on Thursday.
Greece has vowed to do whatever it takes to check its vast deficit, responding to a beating on markets unnerved by Fitch Ratings cutting Greek debt to BBB+ with a negative outlook, citing fiscal deterioration in the euro zone's weakest member.
Despite Tuesday's downgrade, the first time in 10 years a major ratings agency put Greece below an A grade, the chairman of the Eurogroup of euro zone finance ministers said Greece would not go bankrupt and so would not need help from EU states.
"I completely exclude a state bankruptcy of Greece," Jean-Claude Juncker told reporters on the sidelines of a meeting of the conservative European People's Party (EPP) in Bonn.
Markets' nerves were further tested on Wednesday when another ratings agency, Standard & Poor's, revised its credit outlook on Spain to negative and said it risked a downgrade if the government does not take tough action.
In Vienna, European Central Bank Governing Council member Ewald Nowotny dismissed any prospect of a euro zone break-up.
Asked whether there was risk of the single European currency area breaking up because of Greece, Nowotny said: "No, I do not see this in any way."
"An exit or something similar from the euro zone would be totally unrealistic for Greece, and also not doable," he added during a panel discussion in Vienna.
He added that joining the euro was not a panacea for new countries, and it was not the ECB's responsibility to step in and rescue troubled members.
Greece has faced harsh criticism over its credibility and increasing borrowing costs since a new Socialist government revealed the budget deficit was twice as big as previously forecast and would reach 12.7 percent of GDP this year.
SOROS SOOTHES
The premium investors demand to hold Greek government bonds rather than euro zone benchmark German Bunds fell after the comments from Nowotny and another ECB official, and from billionaire financier George Soros.
Soros said he was sure the Greek government would not be allowed to default on its debts despite growing budgetary difficulties and market concerns.
"There has to be pressure on Greece to put its house in order but I'm sure that Greece will not be allowed to default. The same applies to the United Kingdom," Soros told Sky News television.
In Luxembourg, ECB Governing Council member Yves Mersch said he felt confident the Greek authorities were aware of the gravity of the situation, and that they would put in place necessary measures.
The situation in Greece "shows the importance for countries that are in a monetary union to have the necessary discipline to respect established budgetary rules", Mersch said.
Greek Finance Minister George Papaconstantinou on Wednesday reaffirmed his pledge to cut the budget gap from an expected 12.7 percent of GDP this year to 9.1 percent in 2010.
(Additional reporting by Matthias Inverardi and Antonia van de Velde in Luxembourg and Mike Dolan in London; Writing by Paul Carrel; Editing by Victoria Main)