The Washington Post’s Liz Sly and David Ignatius look back at the bloody Syrian civil war--thousands killed, a country in ruins and borders breached by a tide of refugees. What will the future hold for the Syrian people and the al-Assad regime, and how does the U.S. fit into that picture? (Jason Aldag/The Washington Post)

Secretary of State John Kerry met with British Foreign Secretary William Hague and leaders of the Syrian opposition today in London. Kerry did not say exactly whether he is planning on providing the rebels with more assistance:

Kerry had strongly hinted Tuesday that the Obama administration is edging toward a widening of support, saying that the stalemate in Syria leaves “no choice” but to increase pressure on Syrian President Bashar al-Assad from outside. ...

Syria is the main subject on the agenda at a dinner meeting of foreign ministers Wednesday. Britain, the host, has already announced it will provide extensive battlefield support to the rebels, including body armor, and may expand aid to include armored vehicles. France also plans wider battlefield aid.

Diplomats have hesitated to give arms to the opposition because of worries that those weapons might pass into the control of terrorists or extremists. Tensions among rebel groups with differing worldviews have already led to violence and will likely cause more:

Many Syrians are bracing for what they fear will be another war, between the relatively moderate fighters who first took up arms against the government and the Islamist extremists who emerged more recently with the muscle and firepower to drive the rebel advance . . .

Interactive Grid: Keeping track of the conflict in Syria through videos, images and tweets.

“Fighting is unavoidable,” said Abu Mansour, a commander with the rebel Free Syrian Army’s Farouq Brigades, whose men clashed last month with those of the extremist Jabhat al-Nusra movement in the border town of Tal Abiyad, one of several instances in which the tensions have erupted into violence. “If it doesn’t happen today, it will happen tomorrow.”

Adding to the concerns of Syrians and others, Jabhat al-Nusra publicly announced its relationship to al-Qaeda today, the Associated Press reports:

Abu Mohammad al-Golani, head of Jabhat al-Nusra or the Nusra Front, confirmed his rebel group was tied to al-Qaida in Iraq in an audio message posted on militant websites. . .

Nusra Front, which has welcomed militants from across the Muslim world into its ranks, has made little secret of its links across the Iraqi border. But until now, it has not officially declared itself to be part of al-Qaida.

In the recording, al-Golani acknowledges his followers receive assistance and training from al-Qaida in Iraq.

The Syrian group, which wants to oust Assad and replace his regime with an Islamic state, first emerged in a video posted online in January 2012. Since then, it has demonstrated its prowess — and ruthlessness — on the battlefield.

The war has displaced as many as a million people already, but Iraqi refugees there who fled from the violence in their own country have suffered particular hardship:

There are some 480,000 Iraqi refugees in Syria, according to government estimates, many of whom fled Iraq to escape exactly the same kind of indiscriminate violence that is spreading across Syria. . .

Between last summer and the first months of this year, some 70,000 Iraqis headed back home, according to figures from the United Nations High Commissioner for Refugees. During approximately the same period, as violence has flared in Iraq, some 41,000 Iraqis entered Syria.

The numbers indicate a seesaw movement of people caught between two countries wracked by vicious sectarian wars that are increasingly spilling over their borders.