Republicans in the House of Representatives increased their pressure on the Obama Administration on Tuesday over the September 11 attack on the American consulate in Benghazi, Libya, sending a strongly worded letter (PDF) to Secretary of State Hillary Clinton and ordering her to cooperate with the Congress.

The House Committee on Oversight and Government Reform, headed by Republican congressman Darrell Issa, has opened up its own investigation into the attack with a special focus on why security at the consulate was so weak prior to the assassination of Ambassador J. Christopher Stevens.

Issa, in his letter and an interview with CNN, alleged that the administration missed a series of warning signs before the consulate attack occurred, including at least two prior assaults on the Benghazi mission. Issa also pointed out that employees in Benghazi repeatedly requested added security for the compound but were denied such resources by officials in Washington DC.

If that allegation proves to be true, it would be a bombshell that President Barack Obama may find hard to contain. The White House is already facing a litany of criticism over its public messaging about the attacks. Members of Congress and the national media have openly questioned whether the administration distorted the facts surrounding the Benghazi assault to maintain popular just six weeks before the presidential election.

Reports that have come out over the past few days indicate that intelligence officials picked up information mere hours after the attack about possible Al Qaeda involvement. Administration officials, however, stuck to the argument that the incident in Benghazi resulted from anger over an anti-Islam film.

The claims and counterclaims could hardly come at a worse time for the president. National polls show an extremely close election with key battleground states still up for grabs. Republican Mitt Romney and his campaign have used the Benghazi fallout as an opportunity to hammer the incumbent on his foreign policy where just weeks ago, this was Obama’s strong suit. Now, his “tough on terrorism” mantra is challenged, both inside and outside the government.

The president has another difficult decision to make on Libya soon: how to respond to the attack, a dilemma that is compounded by uncertainty over the new Libyan government’s support for further military action.