CANBERRA, Australia—Australia offered to send urgently needed energy supplies to Ukraine to help outflank Russian curbs on coal shipments to its smaller neighbor that have contributed to blackouts across the country.

Prime Minister Tony Abbott said resource-rich Australia was ready to sell coal and uranium shipments directly to Ukraine, whose president, Petro Poroshenko, is on a three-day state visit here. Mr. Poroshenko and Mr. Abbott also pledged closer diplomatic and trade ties following the downing earlier this year of...