Police and troops roll through Jakarta's streets
But a showdown could come earlier because President Wahid has threatened to declare a state of emergency unless the impeachment process is abandoned by 1800 (1100GMT) this Friday.
Assembly leaders have said the MPR will convene within hours if Mr Wahid carries out his threat, raising fears that his supporters and opponents could take to the streets.
Evacuation plans
About 6,000 police and troops with armoured cars, fast troop carriers and helicopters moved into position to protect the parliament complex on Tuesday.
About 42,000 security personnel are expected to be on Jakarta's streets for 1 August.
A police spokesman said there were plans to evacuate assembly members should violence erupt.
Jakarta Police spokesman Anton Bahrul Alam told Reuters news agency: "The head of the parliament and the MPR as well as the president and the vice president will be evacuated by helicopter."
Other members would be moved in police convoy to the Jakarta and national police headquarters, a few kilometres from parliament.
'Shoot-to-wound'
The Jakarta-based website Detikcom reported a police commander as saying demonstrators trying to push past an inner circle of troops guarding the parliament would be "shot below the knees" with live ammunition.
President Wahid has repeated his refusal to quit, saying he will remain in power until the end of his term.
"There is no such word as resign in my dictionary," he said from North Sulawesi. "I must stay on until 2004."
Impeachment
The MPR insists that Mr Wahid must deliver an accountability speech on 1 August to explain the alleged failures of his administration.
If the body - which is dominated by the president's enemies - fails to accept the report, the president would have to step down.
But Mr Wahid says the assembly, which elected him in September 1999, does not have the constitutional right to demand such a speech before the end of his five-year term.