Federal investigators are back from an overseas fact-finding trip armed with new evidence against a Brooklyn man charged with trying to join Islamic militants abroad, prosecutors said yesterday.

Betim Kaziu, a US citizen, allegedly sought jihadist training and weapons from Islamic militants.

Prosecutors went to Kosovo last month to interrogate a witness about Kaziu’s activities before his August 2009 arrest. That testimony is part of a letter prosecutors sent to Judge John Gleeson.