Hedegaard announced Friday she would represent the EU during a Pacific Islands Forum next week in the Marshall Islands.
She said the focus of this year's meeting will be on climate change.
"It is my ambition to make the European Union and the Pacific region partners in advancing the global climate-change agenda," she said in a statement. "The Pacific region can count on Europe's climate cooperation and ambition."
European leaders are debating climate policies for 2030 that would expand on goals for emission reductions and renewable energy use for 2020.
Rising sea levels, which may be due to declining polar ice levels, are threatening low-lying regions like Micronesia and the Marshall Islands.
Marshall Islands President Christopher Loeak issued a plea for attention to the issue during an address last year before the U.N. General Assembly.
Hedegaard said working alongside Pacific region partners would help with comprehensive efforts to combat climate change.
"There is no time to lose if we want to avoid that devastating climate-driven disasters become the new normal,'' she said.