(AP) - The nation's federal transportation agency is criticizing a plan to build a new rail tunnel under the Hudson River.

In a letter Friday to New York and New Jersey officials, the deputy administrator of the Federal Transit Administration says a recent funding proposal by the states raises "serious concerns."

Deputy Administrator K. Jane Williams also writes the states assume a 50-50 funding agreement between them and the federal government where none exists.

President Donald Trump is expected to announce his infrastructure plan next month, and it's not clear where the $13 billion project fits in.

The existing tunnel is more than 100 years old and suffered damage during Superstorm Sandy.

The bi-state development corporation overseeing the project said Friday it's confident Trump will engage with the project in 2018.