By Jim Muir
BBC News, Beirut
Opposition activists in Lebanon called off a strike late on Tuesday, after the imposed action paralysed the country and led to widespread violence in which at least three people died.
There is a very real danger of a huge explosion of sectarian strife
There is no sign of agreement on the issues which prompted the strike, notably the demand by Hezbollah and its opposition allies - including several Christian factions - for a greater share of power and early elections.
Hezbollah and its allies in the opposition had left open the possibility that the strike might be open-ended.
But after assessing its results, they decided to call it off, describing it as "a great success", but warning that steps "with an even greater impact" would be launched, if the government failed to heed the warning.
There have been no explicit statements as to why the strike was lifted.
But part of the explanation must surely be awareness all round of the very real danger of a huge explosion of civil strife with highly sectarian content if the crisis went on unchecked.
The clashes that broke out, in both Christian and Muslim areas, abruptly re-ignited decades-old rivalries and feuds between different factions, some of which now support the government, and others the opposition.
In areas north of Beirut, for example, Christian militants supporting the maverick former army general, Michel Aoun, who is allied to Hezbollah, and others supporting Suleiman Franjieh, a northern warlord close to Syria, tried to block the roads.
But they were confronted by angry youths mobilised by the Lebanese Forces, the pro-government Christian faction headed by the strongly anti-Syrian former militia chief, Samir Geagea.
In densely-populated parts of south-central Beirut where Sunni and Shia populations overlap, there were also fierce clashes between Hezbollah supporters and Sunni youths.
Saudi Arabia and Iran
Sunni-Shia tensions have been rising sharply in the rapidly-polarising Lebanese political crisis.
Pro-government groups opposed to Hezbollah and its opposition allies openly warned that if the Lebanese army and security forces failed to re-open the blockaded roads, they would do the job.
This reinforced fears that if the strike went into a second day, the sticks and stones of day one would be replaced by the guns which most people have in their homes, making serious bloodshed and spiralling civil conflict a real possibility.
Co-operation between Saudi Arabia and Iran may defuse the situation
Beirut newspapers are also reporting highly significant co-operation between Saudi Arabia and Iran, to defuse the situation and reduce sectarian tensions.
The Saudis, regarded as the custodians of Sunni Islam, are closely linked to the Siniora government in Beirut, while Iran - the world's only Shia Islamic republic - has close ties with Hezbollah and with Syria, which has great residual influence in Lebanon.
Riyadh and Tehran have been co-ordinating closely on regional affairs recently. The chief Iranian security official, Ali Larijani, was recently in Riyadh, while his Saudi counterpart, Prince Bandar ibn Sultan, is currently visiting Tehran.
The Iranian and Saudi ambassadors in Beirut are reported to have played a major role in bringing about the decision to call off the strike.
If so, this would be an encouraging development, in a region where sectarian tensions between Sunnis and Shias have been rising sharply, notably in Iraq.
Similar co-operation between the two regional powers could help ease the worsening sectarian strife in Iraq.
As with its ties with Hezbollah in Lebanon, Iran has developed strong links with many of the Shia factions in Iraq, while Saudi Arabia is influential with Iraqi Sunnis on both a religious and tribal level.
If Iran and the Saudis have indeed played a key role in pacifying Lebanon, it is not clear to what extent that initiative was supported or condoned by the US, which under George W Bush strongly backs the Siniora government and tends to see it in black-and-white terms as a bulwark against the region's "terrorists" - a label it applies freely to Hezbollah.
Sunni-Shia tensions are growing sharply in Lebanon
The same question would hang over any Saudi-Iranian initiative to help calm Iraq - something that the Americans desperately need if they are to extricate their forces without triggering chaos.
Most of the signs are that Iran does not see it as in its own interest to have anarchy prevail on its western border.
But whether it would co-operate in a lasting move that would serve American interests without an equivalent favour is another question.
Some regional analysts believe that many of the area's problems - in the Palestinian territories, Lebanon, Iraq and elsewhere - will not be fundamentally settled until the Americans and Iran reach a strategic understanding.
That would clearly have to include a resolution of differences over Tehran's nuclear ambitions, an issue on which Washington has taken an unbending stand.