Portugal was put on notice that its credit rating could be cut and fellow euro zone debtor Spain had to pay more to issue new debt on Tuesday, suggesting the currency bloc's crisis will rage unabated in 2011.

China, the world's new economic powerhouse, urged European policymakers to demonstrate as a matter of urgency that they can contain and then rectify the euro zone's debt problems.

Ratings agency Moody's said it may cut Portugal's rating by one or two notches within three months, citing weak growth prospects as the government seeks to cut its debt, and climbing borrowing costs, although it said its solvency was not in question.

The likely deterioration in debt affordability over the medium term and ongoing concerns about the economy's ability to withstand fiscal consolidation ... mean its outlook may no longer be consistent with an A1 rating, said Anthony Thomas, Moody's lead analyst for Portugal.

The cost of insuring Portuguese sovereign debt against default rose in response and the euro slipped.

Spain cleared its final debt sale of the year, but predictably had to pay a higher price and analysts warned of tough times ahead in 2011.

The yield on Spain's three month treasury-bill issue rose to 1.804 percent from 1.743 percent on November 23, while six-month paper cost 2.597 percent, up from 2.111 percent.

All in all it's a reasonable result in current conditions, if far from impressive. It's going to be testing times for Spain, Portugal and even Italy heading into 2011, said Orlando Green, analyst at Credit Agricole.

A pre-Christmas market lull has taken some of the heat off peripheral euro zone debt but the crisis will surely flare up again in 2011 until or unless policymakers act decisively.

Already this month, Moody's has put Spain and Greece on review for possible downgrades and cut Ireland's rating by a savage five notches, while Standard & Poor's said it may cut Belgium's debt rating next year. Analysts said markets were pricing in even more doom for the euro zone's weaker members than the ratings agencies.

Really the rating agencies are playing catch up with events and arguably they've got a long way to go to get back up to speed -- they've been very much a lagging indicator throughout the crisis, said Chris Scicluna, deputy head of economic research at Daiwa Capital Markets.

European Union leaders failed, at a summit last week, to agree any specific new measures to stop contagion spreading from Greece and Ireland, which have received EU/IMF bailouts, to other high-deficit countries such as Portugal and Spain.

But they did agree to create a permanent financial safety net from 2013 to handle future crises, which may require bond investors to share some of the pain.

Olli Rehn, the EU's economic and monetary affairs commissioner, told Reuters Insider the debt crisis was akin to a forest fire which the EU was determined to contain.

We will do whatever it takes to safeguard the financial stability in Europe, said Rehn.

The prospect that bond investors may have to take a hit on distressed euro zone debt was brought sharply back into focus after a group of subordinated creditors in stricken Anglo Irish Bank agreed to take an 80 percent writedown on the value of their holding, successfully concluding the nationalized lender's debt restructuring plan.

CHINA CONCERNED

China, which has invested an undisclosed portion of its $2.65 trillion reserves in the euro, said it backed steps taken by European authorities so far but made clear it would like to see the measures having more effect.

We are very concerned about whether the European debt crisis can be controlled, Chinese Commerce Minister Chen Deming said at a trade dialogue between China and the European Union.

We want to see if the EU is able to control sovereign debt risks and whether consensus can be translated into real action to enable Europe to emerge from the financial crisis soon and in a good shape.

The European Central Bank has been buying Portuguese and Irish government bonds to shore them up but not in the size analysts say is needed to give the markets pause for thought.

Executive Board member Juergen Stark was quoted on Tuesday as saying the ECB's emergency asset purchase program would remain relatively modest, and based on the principle that all euro zone states are responsible for their own finances.

By no means will we reach the dimensions of other central banks (with bond buys), Executive Board member Stark told the German daily Boersen-Zeitung. We will also not change the current character of the program.

A bailout of Portugal is widely expected but a similar rescue for Spain would stretch EU resources to the limit.

Moody's said if Lisbon sought international help, it would ease short-term uncertainties, but would raise concerns about medium-term access to private market funding.

(Additional reporting by Langi Chiang and Kevin Yao in Beijing and Gergely Szakacs in Budapest, writing by Mike Peacock; editing by Susan Fenton)

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