A year and a half after violent protests saw Bolivia's President Gonzalo Sanchez de Lozada ousted, his successor Carlos Mesa now says he has had enough of the protests and will resign.
Thousands turned out to urge Carlos Mesa not to resign
The BBC News website looks at the issues behind the continuing political and social turmoil in Bolivia.
Q: Why has President Mesa threatened to resign?
President Mesa has been struggling to keep the lid on a nation simmering with tensions. Despite his conservative political background, Mr Mesa has throughout his tenure been forced to listen to the demands of left-leaning social movements, which demonstrated their power when they drove his predecessor Gonzalo Sanchez de Lozada ("Goni") out of office in October 2003.
In recent weeks, Mr Mesa has bowed to demands to cancel the contract of a French-owned water company in the city of El Alto and partially rolled back fuel price rises, following protests in several parts of the country. He also gave in to demands from the elite in the south-eastern province of Santa Cruz to hold a referendum on autonomy for the oil-rich region.
Now faced with escalating protests aimed at making international energy companies pay much higher tariffs to exploit Bolivia's natural gas reserves, Mr Mesa says he has had enough of being held to ransom by protesters.
Q: So is this the end of Mr Mesa?
Mr Mesa's pledge to resign, though sudden, was not a surprise to many commentators, who predicted he would not be able to sustain his grip on power with all the different demands placed on him.
However, Mr Mesa retains significant support among Bolivians, who value his position as a political independent trying to steer the country through its political upheavals. Hours after he announced he was going, thousands of Bolivians gathered in several cities to urge him to stay.
This may prompt Congress to reject Mr Mesa's resignation. Congressional approval is required by Bolivia's constitution before it can take effect.
Mr Mesa's opponents, from both the left and right, accuse him of using the threat to resign simply as a gambit to consolidate his power.
Q: Who would replace Mr Mesa?
In the absence of a vice-president, the constitution dictates that Mr Mesa should be replaced by the Senate president Hormando Vaca Diez in the immediate term. He has previously called for Mr Mesa to "start governing" - widely interpreted as a call for Mr Mesa to reverse his previous refusal to use force to quash protests.
But in the long term, commentators suggest Mr Mesa's resignation might herald a challenge for the leadership by Evo Morales, the leader of Movement Towards Socialism (MAS), the second biggest force in Congress.
Mr Morales' party won 19% of the vote in recent municipal elections - the largest single share - but he remains a divisive figure unpopular with Bolivia's middle classes, its business elite and in Washington. His accession to power would by no means assure an end to the national strife.
Q: What is the background to the struggles in Bolivia?
Bolivia has been a democracy since 1982 after decades of political instability and repeated military coups. But during that time, inequalities of wealth have increased and there has been no reduction in poverty.
This has radicalised Bolivia's impoverished indigenous Indian majority, who feel that the economy has been run for the benefit of a wealthy elite.
As a result, ingrained hostility to giving up control over the natural gas reserves - seen as Bolivia's last big natural resource - has now combined with the Bolivian masses' wider sense of economic exclusion to produce a socially explosive mixture.
In recent years, social movements from within this indigenous majority have been emboldened by several victories, including victory in a campaign to force out a private water consortium in the city of Cochabamba and, of course, the overthrow of President Sanchez de Lozada in the struggle over gas.
Nationalism has also played a part. A plan to export the natural gas through a pipeline running through Bolivia's traditional enemy Chile galvanised the campaign against it, and Bolivians are also deeply suspicious of plans to "sell off" resources to foreign companies.