A senior lecturer in defence and security studies at Massey University says the historic pact signed between Australia and Tuvalu follows the security arrangement the Solomon Islands signed with China last year.
However, the Tuvalu government said its "doing everything" to "maintain our identity in the surface of this planet".
The Australia-Tuvalu Falepili Union treaty allows people in Tuvalu facing displacement from climate change "a special human mobility pathway" to settle in Australia.
280 people a year will be offered special pathways to live, work and study.
In return, Australia will have effective veto power over Tuvalu's foreign security arrangements.
Dr Anna Powles told RNZ's Morning Report said the deal goes "against Pacific agency".
"For Australia, this is inherently about strategic denial and deterrents in the region. So, effectively the right to veto Tuvalu entering into any other type of security or defence partnership or arrangement with any other country, she said.
Dr Powles said the pact also goes against Pacific regionalism.
"This type of arrangement swims against the currents of self-determination and Pacific agency which is very much at the heart of Pacific regionalism."
Tuvalu PM 'very happy'
However, Tuvalu's Prime Minister Kausea Natano told RNZ Pacific he is "very happy" following the reveal of a treaty with Australia.
"I'm pretty sure I'm representing all of Tuvalu's appreciation of Australia's response to our request for support," Kausea siad.
Natano said Tuvalau will aim to "negotiate" similar treaties with other Pacific nations, including New Zealand and Fiji, to "help us" if it is for the advancement of the Tuvalu people.
"We're doing everything we can to give confidence to our people and maintain our integrity, our culture, our traditions, our heritage. We really want to maintain our identity in the surface of this planet," he said.
Natano said he would work with the Australian government to address concerns to reduce fossil fuel usage through the treaty.
"Fossil fuel is the main contributor to global warming but we are aware, of course, that you cannot [phase out fossil fuels] overnight. It's a l ong process, but at least we have somewhere to start.
"By the time that there is an alternative source of energy...everyone will be ready to phase out fossil fuel."
The two parties will finalise the document over the coming weeks.