Merkel used her speech to a congress of her Christian Democratic Union (CDU) party on Saturday to affirm Europe's readiness to impose more severe sanctions on Russia, if it takes further steps to infringe the territorial integrity of Ukraine.

"If the territorial integrity of Ukraine continues to be violated, we will have to introduce economic sanctions," she told fellow members of the CDU as it launched its campaign for the European Parliament elections next month.

"Nobody should doubt this. We are all different in Europe, but we have the good fortune of being united, and together we will take this decision," she said.

Some commentators and analysts have cast doubt on Europe's willingness to follow through on threats to impose tough economic sanctions on Moscow in view of the reliance of some EU countries, particularly in eastern Europe, on Russian gas and trade.

German companies, which have close ties to Russia, have already expressed concern that Europe is taking a too confrontational approach with Russia.

The European Union and the United States have nonetheless responded to Russia's recent annexation of Crimea by imposing some targeted visa bans and asset freezes on particular Russian and Ukrainian figures.

Peaceful strategy

Speaking about her party's campaign strategy, Merkel pledged to bring stability, reforms aimed at boosting the bloc's economic power, and better communication with normal European citizens.

"Europe must be a continent that shows it is possible to be successful by focusing on peace, freedom and prosperity," she said.

She also again stressed that her party was against mutualizing European debt.

This theme was picked up by Jean-Claude Juncker of Luxembourg, the lead candidate for Europe's center-right parties at next month's election.

Euro bonds out

In his speech, Juncker, who was long head of the Eurogroup forum of eurozone finance ministers, reassured the congress that he was against euro bonds.

"Let's not be torn apart by those who allege untruthfully that Juncker is not supported by the CDU because he supports euro bonds, " Juncker said.

"If I become European Commission president, there will be no euro bonds. Therre can't be euro bonds because the conditions for covering even a small portion of the debt are not fulfilled."

Juncker had previously, at the height of the EU's debt crisis, supported euro zone bonds, which Merkel and her CDU have always rejected amid fears they could remove incentives for budget discipline.

Fight for hearts

Juncker also said that the center-right must ensure that it is not painted as the party of austerity, with some Europeans blaming public spending cuts and structural reforms as advocated by Merkel for high unemployment and economic weakness in their countries.

"We need to fight against the suggestion that we are responsible for austerity - for all the evil deeds - and the Socialists have a monopoly on the hearts," he said.

"We are as social as the Socialists and we will prove this."

Former Luxembourg prime minister Juncker will also be campaigning for the Commission presidency against German Social Democrat (SPD) Martin Schulz and the Liberal's Guy Verhofstadt.

tj/ipj (dpa, Reuters, AFP)