Guaido's homecoming Monday followed warnings by the United States and other countries to Maduro not to move against his adversary, and he possibly realized arresting his foe could generate more street protests.
Venezuela is wracked by a humanitarian crisis that has seen poverty soar, with an estimated 2.7 million people leaving the country since 2015.
In talks with public sector unions on Tuesday, he has vowed to stage strikes to help bring down the government.
The United States and some 50 other countries have recognized Guaido as the legitimate leader of Venezuela, arguing that Maduro's re-election past year was invalid - partly because popular opposition candidates were barred from running.
National Security Advisor John Bolton said the USA also is putting foreign financial institutions on notice that they will face sanctions if they facilitate "illegitimate transactions that benefit Nicolas Maduro and his corrupt network".
Mr Guaido and his backers say Mr Maduro's re-election previous year was invalid, making the legislative leader interim president.
"In every democratic transition in Latin America there are negotiations, but I just would say it is extremely hard to see how he could play a positive role in a democratic election, " Abrams said.
"Public sector employees, workers, trade unions will not continue cooperating with. a regime that jails and persecutes them", Guaido said at a meeting with unions in Caracas.
"That's ultimately a decision for Venezuelans to make", Mr Abrams said.
Venezuela is gripped by a humanitarian crisis that is expected to worsen as U.S. oil sanctions created to put more pressure on Mr Maduro take their toll.
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'They won't stop us with threats, we're stronger and more united than ever and looking to the future, ' Guaido told his supporters, holding up his passport in a message of defiance to Maduro's government.
Unions from the oil industry, basic services, the public bank and local government took part in Tuesday's meeting, union leader Ana Yanez told AFP.
"The public administration is practically paralyzed".
As part of his challenge, Guaido is attempting to take control of the state bureaucracy, which he considers to have been "kidnapped" by Maduro through blackmail and persecution. "In the town halls, people only go to work 3 days a week and even then barely half the day", said Yanez.
President Maduro finally made an appearance in the late afternoon to lead a military parade paying tribute to his predecessor Hugo Chavez on the sixth anniversary of the socialist firebrand's death.
President Maduro has done this before, calling his own counter-demonstration every time Juan Guaido announces a protest.
Maduro had been active on Twitter earlier in the day, again paying tribute to Chavez.
The U.S. -backed opposition figure has also planned to bring in foreign humanitarian aid, including those from the U.S. through the Colombian border, to allegedly alleviate the country's economic crisis.
Guaido had secretly left Venezuela for Colombia, in violation of a Supreme Court order, to coordinate efforts there on February 23 to send aid into Venezuela.