Johnny Depp's wife Amber Heard pleaded guilty Monday to falsifying immigration documents in a case dubbed the "war on terrier" after she brought her two pet dogs on their private jet into Australia last year.

The case made global headlines last May after Australia's Agriculture Minister Barnaby Joyce threatened to have the pets, Pistol and Boo, put down unless they "buggered off back to the United States".

Two charges of illegally importing the Yorkshire terriers were dropped on Monday in the Gold Coast court.

But Heard admitted a third charge of providing a false document -- her arrival card, which reportedly failed to declare the dogs.

A black limousine dropped the actress-model and Hollywood star Depp, sporting a tie, at Southport Magistrates' Court in Queensland state.

The couple were both in dark jackets and minders escorted them through a media scrum, an AFP photographer said, as supporters shouted "Go Johnny" and "We love you".

Heard gave the court a video clip expressing her "remorse" over the case, the Australian Broadcasting Corporation reported, and offered a "public apology".

Heard blamed Depp's staff for the mix-up saying they were supposed to take care of all the paperwork.

Her lawyer Jeremy Kirk said: "It was a terrible, terrible mistake. There was no attempt to deceive."

She was due to be sentenced later in the day, after a second adjournment was called.

Twelve witnesses were listed to give evidence but it was unclear if Depp would be called on.

The dogs' presence in Australia only came to light when they were taken to a grooming salon long after they arrived.

The animals -- flown by private jet to Queensland, where Depp was filming "Pirates of the Caribbean: Dead Men Tell No Tales" -- were quickly whisked out of the country as the story hit the headlines and spurred the threat from Joyce.

Depp made fun of the incident and later deadpanned, "I killed my dogs".

"And ate them under direct orders from some kind of sweaty, big-gutted man from Australia," he said in September.

But Heard had vowed never to return to Australia before the couple flew in to the Gold Coast early Sunday.

She had reportedly offered to plead guilty to falsifying her arrival card last October if the two other charges were dropped.

But the Department of Agriculture had refused before finally agreeing in court on Monday.

Under strict bio-security laws designed to keep disease at bay, dogs entering Australia from the United States must be declared and spend 10 days in quarantine.

Penalties for contravening the Quarantine Act range from heavy fines to a maximum of 10 years in prison.