Pakistan beat Iran 3-2 in a first-round tie in Islamabad in what was the first Davis Cup match in the country in 12 years.
Hong Kong had challenged the Davis Cup Committee's decision to approve matches in Pakistan, and withdrew following an independent tribunal ruling that the tie should go ahead.
"The ITF regrets and respectfully disagrees with the decision of Hong Kong, China to default its upcoming Davis Cup tie against Pakistan," the federation said.
"The ITF takes the security of all players, team personnel, officials and spectators very seriously. We are entirely confident in the security risk management procedures we have in place."
Pakistan have advanced to the third round of Asia/Oceania group II as a result of Hong Kong's withdrawal and will host the winner of the tie between the Philippines and Thailand.
The case will be sent back to the independent tribunal to determine if Hong Kong have breached tournament regulations.
Pakistan has been largely starved of international sport since armed gunmen attacked a bus carrying the Sri Lankan cricket team in Lahore in 2009. Six players were hurt while two civilians and six security officials were killed in that attack.
A tour by Zimbabwe's cricket team in 2015 was almost disrupted when a suicide bomber killed two security officials near a stadium.
Cricket is by far the most popular sport in Pakistan, but their national team have played all their home matches at neutral venues abroad ever since the 2009 attack.
Earlier this month, several overseas cricketers withdrew from Pakistan's domestic Twenty20 cricket league final after their cricket board announced the match would be held on home soil.
The final, which was the first-ever Pakistan Super League match to be played in the country, went ahead in the eastern city of Lahore on March 5.
(Reporting by Simon Jennings in Bengaluru; Editing by Ian Chadband)
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