President Barack Obama and U.K. Prime Minister David Cameron laid out their broad guidelines for using force against other nations in the context of a wide-ranging opinion piece on Tuesday which touched upon rising democratic movements in the Middle East and the fight against terrorism in Afghanistan.

Obama and Cameron's comments  were published on Tuesday ahead of meetings in London as part of Obama's six-day tour to Europe where he is making multiple stops to help grow the transatlantic relationship with various allies.

We are reluctant to use force but when our interests and values come together we know that we have a responsibility to act, they said.

The leaders' comments come as a coalition of NATO and a select Arab nations  is currently conducting bombings of targets in Libya with the aim of protecting civilians against the regime of Muammar Gaddafi. The Libyan leader had previously prompted to kill dissenters en masse, prompting a pair of joint resolutions in the United Nations, one of which authorized the use of force from the air.

Notably absent in the opinion piece was Syria, where the killing of protestors in has not yet prompted unified calls from international leaders for action in the form of a U.N. resolution.

They want to discuss Syria, Libya, and Egypt, said White House official of Obama and Cameron last week ahead the trip.

Recently, the United States and European Union imposed sanctions unilaterally on Syrian President Bahsar al-Assad and other senior officials.

President Assad now has a choice:  He can lead that transition, or get out of the way, Obama said in a wide-ranging Middle East policy speech last week.

The Syrian government must stop shooting demonstrators and allow peaceful protests.  It must release political prisoners and stop unjust arrests.  It must allow human rights monitors to have access to cities like Dara'a; and start a serious dialogue to advance a democratic transition.  Otherwise, President Assad and his regime will continue to be challenged from within and will continue to be isolated abroad.

In the speech Obama liked Syria to Iranian ally iran in seeking assistance from Tehran in the tactics of suppression.

The pair also tied themselves to the emerging Democracy movements in the Middle East and North Africa.

What we are seeing there is a groundswell of people demanding the basic rights, freedoms and dignities that we take for granted. We all share in their success or failure, they said.

While they said they wouldn't dictate how the change takes place, they vowed to stand with those who want to bring light into dark, support those who seek freedom in place of repression, aid those laying the building blocks of democracy.