An elderly French-Vietnamese woman vowed on Tuesday to pursue her legal fight to obtain compensation for health problems which she says were caused by exposure to the toxic herbicide "Agent Orange" during the war in Vietnam.

Earlier this week, a French court rejected a lawsuit filed by 79-year old Tran To Nga against 14 chemical companies, but she told reporters she would appeal.

"I am disappointed, I am angry, but I am not sad," said Tran To Nga, whose news conference was broadcast on Reuters TV.

"We are going to carry on because our cause is just. Truth is on our side," she added.

U.S. warplanes dropped about 18 million gallons (68 million litres) of Agent Orange - so-called because it was stored in drums with orange bands - between the early 1960s and early 1970s to defoliate jungles and destroy crops.

Tran, who worked as a journalist and activist in Vietnam in her 20s, has said she suffers from effects including Type 2 diabetes and a rare insulin allergy.

Her lawsuit, first filed in 2014, sought compensation from chemical firms including U.S. companies Dow Chemical and Monsanto, now owned by Germany's Bayer.

Those multinational companies had argued they could not be held legally responsible for how the U.S. military had decided to use their product.

So far, only military veterans from the United States and other countries involved in the war have won compensation over Agent Orange. In 2008, a U.S. federal appeals court upheld the dismissal of a civil lawsuit against major U.S. chemical companies brought by Vietnamese plaintiffs.

The United States has said there is no scientifically proven link to support the claims of dioxin poisoning of many Vietnamese plaintiffs.