The Marshall Islands will become the third country to ratify the Paris climate change agreement, after its parliament approved the step on Friday - following two other Pacific Island nations also highly vulnerable to the impacts of the changing climate.
Two Marshall Islands neighbours, Fiji and Palau, completed their ratification processes in February.
At U.N. climate talks in December, some 195 governments agreed to limit global temperature rise to "well below" 2 degrees Celsius above pre-industrial times and to pursue efforts to keep it to 1.5 degrees.
The new Marshallese president and foreign minister plan to go to New York to join an April 22 signing ceremony for the new global deal, organised by the U.N. secretary-general, and deposit the nation's instrument of ratification, a statement said on Monday.
The Paris agreement, due to take effect in 2020, requires at least 55 countries representing at least 55 percent of global emissions to ratify it first.
"By becoming one of the first countries to ratify the Paris Agreement, we have shown our determination to continue to lead this fight from the front," said Marshall Islands President Hilda Heine.
Small island developing states are already suffering the impacts of climate change, including rising seas and worsening extreme weather, and have pushed hard for more ambitious international efforts to reduce planet-warming emissions.
The Marshall Islands was recently put on high alert for widespread flooding caused by king tides.
Meanwhile the government has declared a state of disaster amid worsening drought conditions that could leave the capital Majuro without fresh water in less than three months' time, the statement said.
On Monday, Fiji's government extended for a further month a state of natural disaster in parts of the country struck by Cyclone Winston in February, the worst storm ever recorded in the southern hemisphere.
"The big tasks now are to ensure that the Paris Agreement enters into force as soon as possible, and that governments move quickly to realign their emissions targets with the new 1.5 degree Celsius warming limit the world agreed to pursue in Paris," Marshall Islands President Heine said.
The Marshallese parliament, known as the Nitijela, has also approved the appointment of former foreign minister Tony de Brum - who played an active role in securing the Paris agreement - as the country's new ambassador for climate change.
De Brum will continue to lead the "High Ambition Coalition" that pushed for key elements of the Paris deal, including the 1.5 degree goal.
The coalition is a group of developed and developing countries, including the European Union, the United States and Brazil, that crossed the rich-poor divide and helped ensure the Paris climate conference ended in success, its supporters say.
De Brum intends to call the coalition together again on the sidelines of the U.N. signing ceremony, the statement said.
The next round of the U.N. climate talks will take place in May in Bonn, Germany, where negotiators will start working out how to put the Paris agreement into practice.