The 1.8 billion euros (USD 2.1 billion) in medium-term loans will help Ukraine meet the "critical challenges" it faces and support the political and economic reforms the European Union believes are crucial to its future, said the Commission.
"The Commission has decided to extend its financial assistance" to Ukraine with "an additional sum of 1.8 billion euros", Juncker told reporters in the Latvian capital Riga.
The bloc's 28 members and the European Parliament must still approve the additional loans.
"Ukraine is not alone. Europe stands united behind Ukraine and the reform agenda of the new government," Juncker said in the Commission statement.
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"The European Union has provided unprecedented financial support and today's proposal proves that we are ready to continue providing that support. This is European solidarity in action."
EU foreign policy chief Federica Mogherini later added, "We have also said and will continue to say that the financial assistance is linked to their willingness to make reforms."
The EU has already released 1.36 billion euros in loans to Ukraine to rescue the almost bankrupt Kiev government.
It will send an additional 250 million euros in the spring on the condition that Kiev successfully implement agreed upon reforms.
The EU and international lenders have backed Kiev since the pro-Russian president Viktor Yanukovych was overthrown in February 2014 after he ditched a pact for closer relations with Brussels.
The new 1.8 billion euros in loans could go into effect in 2015 and early 2016.