Just this year alone, 12 vetted refugees have already been indicted in U.S. courts on terrorism charges, a clear indication of the danger America faces once President Barack Obama succeeds in his plan to "import" more than 10,000 Syrian immigrants, Sen. Jeff Sessions (R-Alabama) revealed.

Since 2010, Obama has already allowed more than 200,000 "low-skill migrants" from Central America to enter the United States, who have then disappeared into the nation's growing population of at least 11 million illegal immigrants, Breitbart.com reported.

This year, Sessions and other critics fear that Obama will use all his powers to bring in far more than the 10,000 Syrian refugees he initially agreed to take.

Sessions said he is pushing Republican leaders in Congress to halt its normal practice of giving the president huge leeway in import foreign migrants into the United States because of the danger this will bring to the nation.

Obama has tried to calm restive Americans by saying that the new refugees will be vetted. However, top security officials say the Syrians can't be vetted because the U.S. doesn't know what they were doing in Syria before they applied for refugee status.

Moreover, Sessions pointed out that many of the past terror attempts in the United States were launched not by the Muslim refugees themselves but by their children who grew up in the country. They include the two Chechen brothers who bombed the Boston Marathon, and Anwar al-Awlaki who was killed by a U.S. missile strike when he fled to Yemen after the 9/11 attacks, he said.

The 12 vetted refugees-turned-jihadis that Sessions listed down only cover 2015 and not the many jihadis from prior years.

"This illustrates just how incapable our government is of vetting refugees or predicting post-entry radicalisation," a Capitol Hill aide who requested anonymity said.

"Yet the president wants a completely blank-check [in the appropriations bill] to fund not only all of these existing refugee programmes from across the globe, but to add a permanent Syrian resettlement programme to it — funded directly out of Americans' paychecks and retirement accounts," the aide said.

Sessions' list of refugees-turned-jihadis this year includes Liban Haji Mohamed, a native of Somalia who sources indicate came to the U.S. as a refugee who was indicted on Jan. 29, 2015 in Virginia for allegedly providing material support to the terrorist organisation Harakat Shabaab Al-Mujahidin, also known as Al-Shabaab and Al-Qaeda.

Also among them are seven refugees from Bosnia who were all indicted on Feb. 5, 2015 in Missouri for providing material support to the Islamic State (ISIS) and conspiring to kill Americans.

They also include a Kenyan refugee and a migrant from Uzbekistan who were also charged with conspiracy and attempt to provide material support to ISIS in April and August this year in Minnesota and Idaho, respectively.