More than 50 former government officials and national security and military figures have signed an open letter to Donald J. Trump, urging him to disclose details of his overseas business investments before Election Day.

The letter — signed by dozens of supporters of the Democratic presidential nominee, Hillary Clinton — was drafted as Mr. Trump, the Republican pick who is reported to have extensive overseas entanglements, has refused to release his tax returns.

Michael J. Morell, a former acting director of the C.I.A., and Michael G. Vickers, a former under secretary of defense for intelligence, put together the letter with input from Samantha Vinograd, a former senior adviser to Thomas E. Donilon, a former national security adviser.

“Donald Trump still has not revealed to the American public his international business relationships, even as it becomes increasingly clear that his overseas ties could well constitute significant conflicts of interest when it comes to charting U.S. foreign policy,” the letter reads. “This is unprecedented for a candidate for the nation’s highest office. As such, we are calling on Mr. Trump to disclose, in full, the nature of his business relationships overseas — to include specifically who his business partners are and what and where are his foreign investments.”