CHISINAU, Moldova (Reuters) -U.S. Secretary of State Antony Blinken on Sunday reassured Moldova’s leaders that the United States would rally international opposition to Russian aggression "whenever and wherever" it occurs.

       Speaking alongside Moldovan President Maia Sandu on a tour through eastern Europe in the wake of Russia’s invasion of Ukraine, Blinken also said that the United States supported Moldova's aspirations to join the European Union but that the process would be decided by the EU.

       Moldova says more than 230,000 refugees have crossed its border with Ukraine since the war began on Feb. 24.

       Asked what assurances Washington could give Moldova in light of Russia's aggression toward Ukraine, Blinken pointed to U.S. efforts to mobilize the international response that is isolating Russia and hurting its economy.

       "Whenever and wherever that aggression might appear, we'll do the same thing," he said.

       The United States is not committed to defend Moldova since the former Soviet Republic, like its neighbor Ukraine, is not a member of NATO.

       Sandu is a former World Bank economist who came to power in 2019 and won a larger mandate in elections in July promising closer ties with the West.

       Moldova on Thursday formally applied to join the European Union. The move was likely to rile Moscow, which has an estimated 1,500 troops based in the breakaway region of Transnistria in Moldova’s east.

       Blinken said the U.S. was providing $18 million over the next few years to "strengthen and diversify" Moldova's energy sector. Moldova depends heavily on Russian gas.

       "(Energy) independence and energy security is actually critical to maintaining one's sovereignty and independence," Blinken said.

       At least 120,000 of those who have crossed into Moldova remain in the country of about 2.5 million people, Prime Minister Natalia Gavrilita said in an earlier meeting with Blinken.

       “For a small country like Moldova, this is a very large number” and Moldova will need assistance to deal with the refugees, she said.

       (Reporting by Simon Lewis; Editing by Elaine Hardcastle)