Venezuelan opposition leader Juan Guaido left Caracas with some 80 lawmakers on Thursday on a 800-km (500-mile) trip to the Colombian border where they hope to receive food and medicine to alleviate shortages in defiance of President Nicolas Maduro.

Crowds formed alongside a main highway out of the capital, waving Venezuelan flags and whooping in support, as the convoy of buses departed.

Guaido, recognized by dozens of countries as Venezuela’s legitimate head of state, has pledged to bring in the humanitarian aid by land and sea on Saturday. Guaido invoked the constitution to assume an interim presidency on Jan. 23 and denounces Maduro as an usurper.

“Through this call for humanitarian aid, the population will benefit from the arrival of these goods to the Venezuelan border,” said opposition legislator Edgar Zambrano, as he waited to board a bus in a plaza of eastern Caracas.

Maduro’s beleaguered socialist government denies there is an economic crisis in Venezuela and has said soldiers would be stationed along the country’s borders to prevent potential incursions.

He accuses the Trump administration, which recognizes Guaido and is supporting the relief effort but has levied crippling sanctions against his government, of seeking to force his ouster.

Guaido still has not provided details on how they will bring in the aid. Opposition figures have suggested forming human chains across the Colombian border to pass aid packages from person to person and fleets of boats arriving from the Dutch Caribbean islands.

The United States has sent tons of aid to Colombia’s border with Venezuela, which Maduro has mocked as a “cheap show.” Maduro’s vice president, Delcy Rodriguez, has alleged the aid is poisonous and could lead to cancer.

On Wednesday, Maduro’s socialist administration said it had closed the country’s maritime border with the Dutch Caribbean islands of Aruba, Curacao and Bonaire, after Curacao’s government said it would help store aid destined for Venezuela.

Colombia expelled five Venezuelans from Cucuta for “carrying forward activities which attack citizen security and social order,” its migration agency said in a statement late on Wednesday.

“We know there is interest by the Maduro dictatorship in affecting national security because of coming events,” agency director Christian Kruger added in the statement.