Zimbabwe's parliament began a five-month session on Tuesday that will debate a bill giving President Robert Mugabe room to pick a successor if he were to retire and a proposal to localise foreign-owned companies.

If passed, the bills could tighten Mugabe's grip on power as frustrations grow over a deepening economic crisis and Western powers increase pressure on him to enact political reforms.

The legislative session will be the last before parliamentary and presidential elections next March when Mugabe is expected to seek another five-year term.

Mugabe's ruling party has a technical two-thirds majority in parliament, which gives it room to pass bills without support from the main opposition Movement for Democratic Change (MDC).

Among the bills to be considered is the government's Indigenization and Empowerment Bill, which requires foreign companies to cede 51% of their holding to Zimbabweans.

The bill raises fresh concerns about economic policies in a country with the world's highest inflation rate and severe food, fuel and foreign currency shortages.

Critics say Mugabe's controversial policies, including the seizure of white-owned farms for redistribution to landless blacks, have destroyed the economy, once seen as one of Africa's most promising.

Parliament will also consider a Constitutional Amendment bill seeking to empower parliament to choose a president if a vacancy arises between elections.

Analysts say Mugabe may seek to step down mid-term after nearly three decades in power and would be able to anoint a successor because parliament is dominated by his ruling ZANU-PF.

Government ministers were not available to comment on when the bills would be tabled before the assembly, which is expected to be in session until November.

MDC parliamentary chief whip Innocent Gonese told Reuters the introduction of the two bills could be delayed.

The MDC says amending the constitution would be a sign of bad faith because it is already a sticking point in troubled talks between the opposition and ZANU-PF.

South African President Thabo Mbeki has been mediating between the two sides. Western diplomats say there has been little progress.

The MDC is pressing for a new constitution but it has a minority in parliament and the opposition is weak and divided, leaving Mugabe unchecked.

"With respect to the constitutional amendment bill ... I doubt that could happen today or this week as ZANU-PF might want to wait for a definite conclusion, one way or the other, of the ongoing talks," Gonese said.

"I would say possibly next week, but even then, it looks improbable," he added.