The Australian bowling legend said Friday he was investigating whether he qualified for a German passport so he could play county cricket in England as a non-overseas player.
Howard looked incredulous when asked for his reaction to the report that Warne might renounce his Australian citizenship.
"I would be amazed if Shane ended up doing that -- amazed. So would a lot of Australians," he told reporters.
"What people do with their citizenship in the end is their own business, but I think along with most Australians I'd be amazed."
The 37-year-old leg-spinning great first played for Hampshire seven years ago and has been with the English county since 2004 in his current spell.
He is contracted to the county club until the end of next season, having retired from Test cricket in January with a record of 708 wickets in 145 matches.
English county sides are currently allowed to have two overseas players at present, but that will be reduced to one next summer.
Players holding European Union passports do not, however, count towards the quota.