ATHENS, Greece (AP) — The Greek government launched a new round of negotiations with rescue creditors Monday over the course of the country's latest bailout program, amid highway blockades and angry union reaction to proposed pension reforms that are central to the talks.

Representatives from Greece's European creditors and the International Monetary Fund began talks in Athens with Greek officials. The talks are expected to last the week before pausing and resuming later this month.

In return for money from the country's third bailout, which was agreed last summer and is worth around 80 billion euros ($87 billion), Greece's left-led government has to meet a series of conditions, from reducing spending to enacting wide-ranging economic reforms.

Meeting the targets set will also open up discussions over debt relief — after years of savage austerity, Greece's debt burden still stands at around 175 percent of its annual GDP. The IMF has already said that burden is unsustainable and says Greece needs help, which could include lower interest payments on the debts or further extending repayments way into the future.

One of the main reforms the Greek government has to undertake next is the overhaul of the country's pensions system, which the government has admitted is in a parlous state.

But unions representing groups as disparate as farmers, police, fishermen and lawyers are fiercely opposing the draft reforms, saying they will end up paying most of their income in taxes and social security contributions.

As a result, they are planning a string of protests and strikes this week. On Monday, farmers used scores of tractors to indefinitely block two border crossings with Turkey and Bulgaria, stopping trucks but allowing all other traffic to pass. Other crossings with Turkey and Bulgaria were being sporadically closed, as were highways across Greece.

"We want the government to listen to our demands, because if these measures on pension reform go through, we're finished," said Giorgos Nikolopoulos, a farm protest organizer, speaking a roadblock in central Greece.

Unions have called a general strike for Thursday. Journalists, public transport employees, lawyers and notaries public will also be walking off the job in coming days.