ATHENS, April 7 (Reuters) - Greece's economy can withstand the new challenges that U.S. tariffs pose, Prime Minister Kyriakos Mitsotakis said on Monday, as the country awaits a unified European Union stance on the matter.

U.S. President Donald Trump's sweeping tariff plans hammered global financial markets after he warned foreign governments they would have to pay "a lot of money" to lift the levies that he called "medicine".

The 27-nation EU faces 25% import tariffs on steel and aluminium and cars and unilateral tariffs of 20% from Wednesday for almost all other goods. EU countries are weighing approval of a first set of targeted countermeasures.

"Greece insists on a unified response so that we can be effective on a EU-27 level," Mitsotakis said in a televised speech, before a ministerial meeting on economic policy.

He said the measures would be detailed within weeks.

"The government, in these difficult circumstances, guarantees that the national economy is ready to deal with these new challenges," he said, promising fiscal prudence.

Exports to the United States represent about 4% of Greece's total exports. Mitsotakis said that U.S tariffs on products such as olives, olive oil and genuine Greek feta cheese, which cannot be produced in the United States, were "not very sensible".

(Reporting by Lefteris Papadimas
Editing by Peter Graff)

((lefteris.papadimas@thomsonreuters.com; +30 6944 248134; Reuters Messaging: lefteris.papadimas.reuters.com@reuters.net))