The Treasury says increasing the pension age for the island early wouldn't stop the fund running out.
A report to Tynwald this month says the national insurance fund will run dry by 2047 unless action is taken.
But hiking the pension age to 68 in 2037 rather than 2044 would only give one extra year before the money ran out.
The document suggests a range of options such as increasing NI contributions or scrapping the triple-lock on pensions.