Kevin Rudd’s was one of the best foreign ministers in the business, according to his Canadian counterpart.
Mr Rudd’s diplomatic colleagues have paid tribute to him following his unexpected resignation.
He resigned as foreign minister in Washington on Wednesday while on official duties.
Mr Rudd is en route back to Brisbane and is expected to challenge Prime Minister Julia Gillard on Monday for the Labor leadership.
Canada’s Foreign Minister, John Baird, took to Twitter to express his disappointment “at the departure of a friend, dear colleague and one of the best foreign ministers”.
“@kruddmp was distinguished – always one the smartest and most accomplished minds at the table. A great friend of Canada, I wish him well,” he wrote.
Sweden’s Foreign Minister, Carl Bildt, also sent a Tweet saying he was saddened by Mr Rudd’s resignation and he had been a “good partner on many issues”.