Venezuela's foreign minister has walked out of a meeting of regional diplomats to discuss the South American country's political crisis, as a 17-year-old anti-government protester was killed during clashes with security forces.

The Organisation of American States meeting in the Mexican resort of Cancun again narrowly failed to approve a resolution that would have pushed back against some of Venezuelan President Nicolas Maduro's most radical actions.

The US, Mexico, Canada and several South American nations issued a statement expressing their "disappointment" at the vote, which fell three votes short of the two-thirds majority of the 34 member nations needed for approval.

"What can we say to the sick, who can't find medicines?" Mexican foreign minister Luis Videgaray said of the setback, referring to the medicine shortages Venezuelans are experiencing.

Countries pushing for elections in Venezuela came closer than ever, and Mr Videgaray left open the possibility the Venezuela issue may be brought up in Tuesday's broader meeting of the OAS general assembly, where a simple majority is needed.

Venezuelan foreign minister Delcy Rodriguez stalked out of the meeting, and claimed that more OAS members were considering following Venezuela's example and withdrawing from the regional group, which has been putting pressure on her socialist government to hold timely elections, free political prisoners and scrap a bid to rewrite its constitution.

"Not only do we not recognise this meeting, we do not recognise any resolution coming out of it," Ms Rodriguez said.

She would not say which countries are considering leaving the Washington-based OAS, although Venezuela has received support from other left-leaning governments like Nicaragua, Bolivia and Ecuador.

Some countries had expressed hope at Monday's meeting that they were close to some kind of pronouncement aimed at ending the increasingly bloody political strife in Venezuela, which has left at least 70 people dead and more than 1,300 injured, but the special session ended with no resolution.

As the meeting took place, thousands of protesters took to the streets of the Venezuelan capital, Caracas, to protest against Nicolas Maduro's government. Protesters chanted: "Who are we? Venezuela! What do we want? Freedom!"

Amid the clashes on Caracas's main highway, 17-year-old Fabian Urbina was killed by a bullet wound to the chest, local authorities said without providing more details. Several others were also reportedly shot.

A small knot of protesters also gathered in the rain on a highway outside the Mexican resort complex where the talks were being held, holding signs saying "No more deaths" and "no more hunger".

AP