It's possible, but not advisable.
In publisher use File-Save As to save the document as HTML web page. A
document.htm file and a folder named document_files containing other pages
and images will be produced.
Open a web in FrontPage and import the file and folder.
When Publisher generates HTML files it uses absolute positioning and
excessive images. Text is often placed in images, making the pages very
large (long downloads) and editing outside Publisher very difficult, if not
impossible. It is often easier to rebuild the document from scratch in
FrontPage than use the pages produced by Publisher.
Ron