An Iraqi-born man who entered the United States as a refugee pleaded guilty on Monday in Texas to attempting to volunteer to fight with Islamic State, federal prosecutors said.

Omar Faraj Saeed Al-Hardan, 24, pleaded guilty in a federal court in Houston to one count of attempting to provide material support, specifically himself, to the militant group, the US Attorney's Office for the southern district of Texas said in a statement.

Al-Hardan, who most recently lived in Houston, faces up to 20 years in prison when he is sentenced on Jan. 17, prosecutors said.

The case comes during a US presidential race in which the question of admitting refugees from the Middle East, especially Syria, has become a point of contention between the two leading candidates.

Democratic presidential nominee Hillary Clinton has called for increasing the number of Syrian refugees admitted and said the United States can adequately screen them. Republican nominee Donald Trump has opposed their entry and called for ‘extreme vetting’ of incoming Muslim immigrants.

In the Texas case, federal agents began investigating Al-Hardan in 2014 after he communicated with a California man who he believed was associated with the Syrian Islamist rebel group Al-Nusrah, prosecutors said in a statement.

Al-Hardan in 2014 and 2015, in discussions with a confidential informant, said he planned to travel overseas to support Islamic State, prosecutors said.

He also said he had taught himself to make remote detonators and showed off a circuit board he built as a transmitter, prosecutors said.

Al-Hardan entered the United States as an Iraqi refugee in late 2009, about two years before the start of a civil war in Syria, after spending time in refugee camps in Jordan and Iraq, prosecutors said. He was later granted legal permanent residence.

The arrest of Al-Hardan gained national media attention in January, with Texas Lieutenant Governor Dan Patrick, a conservative Republican, citing it as an indication of why Texas was seeking to block the resettlement of Syrian refugees.

Islamic State, which controls tracts of land in Iraq and Syria, has claimed credit for a surge in global attacks this summer, even as it has been hammered by US-led coalition airstrikes. On Monday, Iraqi forces launched a US-backed offensive to drive Islamic State from the city of Mosul.

President Barack Obama has said refugees are properly screened and vetted.