A Congressional report on jihadist group the Islamic State has said the United States failed to stop its nationals from travelling to Syria and Iraq to join ISIS.   

The report by the Homeland Security Committee said more than 250 U.S. nationals travelled abroad to join ISIS in 2015 alone. Over 25,000 foreigners traveled to Syria and Iraq since 2011 to become ISIS jihadists.

"Of the hundreds of Americans who have sought to travel to the conflict zone in Syria and Iraq, authorities have only interdicted a fraction of them. Several dozen have also managed to make it back into America," the report said, according to Newsmax.

Homeland Security Committee Chairman Michael McCaul warned that the United States faced a grave and growing threat from foreign fighters.

"Sadly, global efforts have failed to stop the flow of these aspiring jihadists into Syria, and we have already seen 'returnees' from the conflict zone come home to America and Europe and plot acts of terror. Even more, those still on the battlefield are radicalizing their peers online and inciting them to launch homegrown attacks," he said in a statement, according to Fox News.

"We have to have a strategy to deal with this: both a military strategy abroad, a political solution, but also a prevention strategy here in the United States to prevent this threat," said McCaul, according to CNN.

The Congressional report, released on Tuesday, came in the backdrop of an anti-ISIS summit chaired by U.S. President Barack Obama on the sidelines of U.N. General Assembly.

Obama, at the summit, said that ISIS poses a threat to the United States and the international community and that all instruments of power will be used to defeat it, a White House statement said.