Islamic State propagandists are becoming "more overt" in their attempts to recruit fighters in Latin America, raising concern that the group will spread to the Western Hemisphere even as it loses ground in Iraq and Syria.

"ISIS and its sympathizers are growing more overt in Latin America," Sen. Joni Ernst, R-Iowa, wrote to President Obama in a Monday letter. "Their increased use of messaging in Spanish and Portuguese, coupled with calls for terror in the region, exemplify ISIS' unwavering determination to change and imbed in new surroundings."

Ernst, a member of the Senate Armed Services Committee, sent the letter in advance of Obama's trip to Peru at the end of the week. He's traveling for an Asia Pacific Economic Summit that will be dominated by talk of trade deals and other issues, but Ernst wants him to prioritize national security.

"With ISIS setting its sights on global expansion, and a history of Islamic extremism in the region, we cannot afford to continue turning a blind eye to these threats emerging right here in our own hemisphere," Ernst wrote.

Terrorist groups have been developing organizations in South America for years, as governments have struggled to control their own countries in the face of opposition from drug cartels, and Arab immigrant populations have provided a recruitment base.

Hezbollah, a Shiite-terrorist group sponsored by Iran, was recognized as the dominant terrorist threat in the region after the 9/11 attacks, but the Islamic State has made inroads more recently.

"You want to spread an extremist message in the Caribbean and recruit fighters for ISIL?" Navy Adm. Kurt Tidd, head of U.S. Southern Command, said in July. "We have a worrisome number of networks engaged in that."

A group of Brazilian jihadists pledged allegiance to the Islamic State in July. And yet, Ernst emphasized, Panama is the only Latin American country to join the U.S.-led coalition against the terrorist group. Ernst urged Obama to "encourage more Latin American countries to join the coalition" when they meet at the APEC summit.

"It should be clear to you by now that I do not support your measuring of our success against ISIS by the land they lose in the Middle East, as it is not an accurate representation of the progress we are making against Islamic extremist groups that wish to do us harm," she wrote.

"I remain firm in my belief that your administration must broaden its horizons to effectively combat the spread of radical Islamic terrorism and I look forward to your response."