Pompey kicked-off their Sky Bet League Two campaign with a 4-1 home defeat to Oxford, but Howe believes they will be challenging for promotion come the end of the season.
"I'm expecting them to be organised, resolute and determined. I know Guy Whittingham has changed the squad a lot but they have some good players," he told the club's official website.
"They had a disappointing result on Saturday, but they have a strong squad and I'm sure they will be there or thereabouts come the end of the season.
"When we played each other last season there was very little between the two teams. We've gone up and they've gone down to League Two, but I don't think the gulf will be that big.
"We will have to do all the little things right and I'm certainly not underestimating Portsmouth. We learnt on Saturday that we need to be at our best to win games."
- Sports & Recreation
- Guy Whittingham
- League Two