A government official said he would announce "an important initiative" at the rally.
Pakistan has not yet officially declared reciprocal moves.
Pakistan yesterday foreshadowed matching India's resumption of full diplomatic and air links with Islamabad, saying it will "soon" announce steps to reduce 17-month old tensions with its nuclear neighbour.
Jamali also had a telephone conversation with U.S. Secretary of State Colin Powell. "He conveyed to Mr Colin Powell that Pakistan will soon announce measures aimed at creating a congenial atmosphere and to promote peace and security which are vital for the region and its people," a foreign ministry statement said.
"Secretary of State Powell assured the prime minister that the United States would continue to make efforts to promote better understanding between India and Pakistan," the Pakistani ministry said.
President General Pervez Musharraf and Jamali had discussed the Indian Prime Minister Atal Bihari Vajpyee's peace overtures at a two-hour meeting on Friday, which was also attended by Kasuri and top foreign ministry officials.
Later Musharraf, speaking at a banquet in honour of Ismaili community spiritual head Prince Karim Aga Khan, said Pakistan stood ready for dialogue with India "anytime, anywhere".
"We seek peaceful resolution of all disputes and differences, especially the core dispute over Jammu and Kashmir and will demonstrate our seriousness," he said.
Musharraf vowed that Islama-bad would leave no stone unturned in confronting extremism and said "in this endeavour Pakistan seeks peaceful co-existence with the entire world, particularly with its neighbours".
Reactions from Pakistan on Friday to the announcement that India would restore air and diplomatic links were upbeat, with Information Minister Sheikh Rashid saying bilateral talks between the arch-rivals "should be soon, as things are moving quite fast".
Both sides indicated Armitage's upcoming trip helped bring them together.
Visits by U.S. officials often lead to a sudden improvement in rhetoric as the nuclear rivals try to avoid being criticised by Washington – and last year, helped pull the two South Asian rivals away from the brink of a war.
The two countries massed troops at their border after India blamed Pakistan for a December 2001 attack by militants on its Parliament. Pakistan denied involvement. Tensions eased after intense diplomacy by the U.S. and Britain.
The main source of friction between the two countries is Kashmir, which is divided between them and claimed by both in its entirety. India and Pakistan have fought two of their three wars over the region since their independence from Britain in 1947.
Militants in Kashmir began fighting for independence or merger with Pakistan in 1989. India accuses Pakistan of aiding the miltants – a charge Pakistan denies.