Venezuelan President Nicolas Maduro called on Barack Obama to “accept the challenge” and hold direct talks, a surprise overture made Friday after days of accusing Washington of plotting his overthrow. The dramatic announcement came after nearly three weeks of often violent anti-government protests in Caracas and other major cities, widely seen as the biggest test to Maduro since he succeeded Hugo Chavez last year. US Secretary of State John Kerry on Friday condemned Venezuela’s “unacceptable” use of force against anti-government protesters, and declined to respond to a call from Caracas for bilateral talks. “The government’s use of force and judicial intimidation against citizens and political figures, who are exercising a legitimate right to protest, is unacceptable and will only increase the likelihood of violence,” Kerry said in a statement.