WASHINGTON — A “foreign fighter surge team” of experts from the F.B.I., the State Department and the Department of Homeland Security met with their Belgian counterparts a month before the Brussels terrorist attacks to try to correct gaps in Belgium’s widely criticized ability to track terrorist plots, American officials said.

The half-dozen experts focused on long-term structural fixes to the Belgians’ failure to share intelligence effectively and to tighten porous borders, but not on providing information about suspected Islamic State operatives. The recommendations, even if accepted, would not have prevented the attacks at the Brussels Airport and in the city’s subway last month, the officials said.

But the gaps addressed in two days of meetings, held at Belgium’s request at the United States Embassy in Brussels, underscore the urgency and the frustration senior American officials say they feel as they prod many European allies to embrace the kind of counterterrorism lessons the United States learned after the Sept. 11 attacks. The American experts have also visited Greece and are expected to travel to France and Germany in the coming weeks, Obama administration officials said.

The team was part of a little-noticed White House plan announced after the Paris terrorist attacks in November to help Western European allies shore up their defenses and borders to avert the next big attack that European and American terrorism officials feared was inevitable.