Senate Democrats beat back, 54-45, a Republican attempt Thursday evening to prevent accused 9/11 terrorists from being tried in U.S. courts.

The vote was the latest attempt by Republicans to make it more difficult for President Barack Obama to follow through with his plan to close the Guantánamo Bay, Cuba, military prison and try suspected terrorists in the United States. However, the amendment, sponsored by Sen. Lindsey Graham (R-S.C.), would only affect about six of more than 200 detainees picked up in the war on terrorism, Graham’s office said.

Four Democrats and one Democratic-leaning Independent — Sens. Maria Cantwell (D-Wash.), Joe Lieberman (ID-Conn.), Blanche Lincoln (D-Ark.), Mark Pryor (D-Ark.) and Jim Webb (D-Va.) — voted with all 40 Republicans to support the amendment, which was killed by a motion to table it. Both Lieberman and Webb co-sponsored the amendment with Graham and Sen. John McCain (R-Ariz.). The amendment was offered to the Commerce-Justice-science appropriations bill.

Republicans contend that during previous terrorism-related trials, information has come out that has tipped off al-Qaida leadership to U.S. surveillance tactics. Those revelations caused the terrorist organization to identify leaks and stop using those modes of communication, they contend.

McCain said the 9/11 conspirators committed war crimes and as such should be tried by the military.

“It is a war crime that was committed,— McCain said on the floor Thursday. “It’s important that we call things what they are and not gloss over the essence of these events, even though they occurred eight years ago.—

Senate Minority Leader Mitch McConnell (R-Ky.) said “there is no question— that accused 9/11 conspirator Zacarias Moussaoui considers himself an enemy combatant, and McConnell quoted Moussaoui as saying U.S. military personnel “should expect that people who are at war with [them] will try to kill [them]. I will never cry because an American bombed my camp.—

But most Democrats contend terrorism prosecutions are routine and safe.

“One hundred and ninety-five terrorists have been prosecuted in our courts since 9/11,— Majority Whip Dick Durbin (D-Ill.) said on the floor Thursday. “Three have been prosecuted by military commissions. But the offerers of this amendment want to tie the hands of our Department of Justice and tell them you cannot spend a penny, not 1 cent, to pursue the prosecution of a terrorist in an American court.—

During debate on this year’s wartime supplemental spending bill, Democratic leaders in both chambers initially moved to prohibit detainees from being moved to the United States for any purpose, but they softened that language to allow for civilian trials.

Obama has set a January 2010 deadline for the closure of Guantánamo Bay, but White House aides have acknowledged in published reports that the deadline may slip, given the administration has not yet produced a comprehensive plan for where to house the suspected terrorists that were picked up in the wars in Afghanistan and Iraq.