BOSTON, July 28 (UPI) -- U.S. Sen. John Kerry has agreed to pay a $500,000 Massachusetts use tax on his $7 million yacht even though he says he plans to dock it in Rhode Island.

The Massachusetts Department of Revenue has been investigating reports the sloop, registered in March, has been spending a lot of time in Massachusetts waters, the Boston Globe reported.

"We've reached out to the Massachusetts Department of Revenue and made clear that, whether owed or not, we intend to pay the equivalent taxes as if the boat's home port were currently in Massachusetts,' Kerry, D-Mass., said. "That payment is being made promptly.'

Jodi Seth, a spokeswoman for the senator, said the yacht, the Isabel, was built in Rhode Island and docked at the Newport Shipyard for legitimate reasons, and not because Rhode Island has become a haven for expensive boats. Massachusetts boat buyers must pay sales tax for transactions in state and a 6.25 percent use tax for boats bought elsewhere and used in the state as well as annual excise taxes.

Rhode Island, long a haven for sailors, ended its boat taxes in 1993.