Democratic senators renewed their efforts Friday to ease the path for Filipinos who fought for the United States in World War II and are now U.S. citizens to obtain immigration visas for their adult children.

Minority Leader Harry Reid (D-Nev.) and Sen. Mazie Hirono (D-Hawaii) introduced legislation that would exempt up to 20,000 individuals from annual worldwide U.S. visa caps established by Congress that have led to lengthy backlogs -- up to two decades in the Philippines.

An estimated 250,000 Filipinos fought on behalf of the U.S. military during the war, and about 26,000 received citizenship under the 1990 naturalization act signed by President George H.W. Bush. But the benefits did not extend to their adult children. Many of the estimated 6,000 aging veterans still living in the United States -- now in their 80s and 90s -- have been frustrated about the long waits to gain immigration papers for them. The Washington Post reported on the issue in January.

Hirono and other Democratic lawmakers have introduced similar bills previously, including in 2013, but none has advanced through Congress. Two years ago, the measure was included in a comprehensive immigration bill approved by the Senate, but the Republican-controlled House killed that legislation by refusing to vote on it. It is unlikely that the GOP-majority Congress will move the new Filipino immigration bill forward this term.

"Time is running out," Hirono said in a statement. "We as a nation made a promise to these veterans that must be kept."