Representatives from the five parties in the power-sharing Executive will take part in discussions, facilitated by a senior civil servant, for three days at Stormont over flags, parades and dealing with the past.
Another three-day round focusing on these issues is scheduled for next week.
Meanwhile in London, the First Minister Peter Robinson and deputy First Minister Martin McGuinness have met with Prime Minister David Cameron.
Wednesday's talks come after all-party negotiations chaired by US diplomat Dr Richard Haass, ultimately failed to deliver consensus last year.
They also come ahead of the biggest day of the main loyalist marching season, the Twelfth of July.
Trouble broke out last year when the watchdog banned participants from passing the Ardoyne shop fronts.
On Wednesday afternoon, Orangemen were granted permission, with restrictions, to parade past the disputed section of the Crumlin Road on the morning of the Twelfth.
The decision on the more contentious evening parade back along the road, which was banned last year, is due on Thursday.
Arriving at Stormont earlier, Sinn Fein's lead negotiator Gerry Kelly said his party was "setting the scepticism aside" and were hopeful for progress.
These three toxic issues need sorted out and we have a chance of doing that.
Gerry Kelly, Sinn Féin MLA
"The pressure's on and the pressure should be on," the MLA said.
SDLP leader Alasdair McDonnell said it was time to "get things sorted out".
He also called on the UK and Irish governments to become directly involved in the process.
"We have been working around this for long enough," he said.
"We have had four months of Haass, we have had six months of leaders' talks, we know what the issues are and we now need a solution.
"The SDLP are there to ensure we do what is necessary in the next two or three weeks to solve and bring the thing to a conclusion."
We're talking about controversial parades and protests and others don't want to talk about them and take them on. But that's their choice.
Tom Elliott, UUP MLA
At the lunchtime break in talks, UUP negotiator Tom Elliott accused other parties of refusing to confront specific issues, such as the disputed north Belfast parade.
"We are talking round things as opposed to talking about specific issues," he said of the opening session of negotiations.
"To me, we need to deal with the hard issues. There are a lot of difficult issues out there at the moment and we need to talk specifically about them.
DUP negotiator Jonathan Bell also stressed the importance of resolving the disputed over the parade route.
"We are very clear that the success of these talks will be based upon tolerance and respect," he said.
"We look very much towards recent issues of parading, we look at the deficit there is within nationalism - the lack of tolerance, the lack of respect, the lack of accommodation."
While Alliance party leader David Ford expressed hope that consensus could be achieved at the end of the six days of talks.
"We need to have an agreement on the past for the sake of the victims and because it is costing huge sums to the justice system, we need to deal with the contentious issue of flags, which are all across Belfast annoying people, and we also need to deal with the resolution of parades," he said.
"Those, if people are willing, can be resolved in six days of intensive talks and it is now up to others not to demand that they get their own way on everything, but that they agree an honourable compromise."
While these talks got underway, First Minister Peter Robinson and deputy First Minister Martin McGuinness were in London to meet Prime Minister David Cameron.
Emerging from the meeting, Mr Robinson took the opportunity to criticise the Parades Commission's for decisions in recent weeks but added that the unionist leadership would "channel that anger" in a way that was "peaceful and political".
He referred to a determination on a parade planned for Portadown last weekend that was initially permitted only for the watchdog to reverse its decision.
Mr Robinson said: "A real effort has to be made to ensure that we don't have violence on the streets.
"I abhor violence on the streets and the cause of violence as well, because very often the cause is stupid decisions that are made by bodies that are appointed to make sensible decisions.
"You cannot have a body that takes a decision one day to allow a parade to go down a road, changes its mind the next day and says it can't go down a road, changes their minds to say they'll have a review, changes it again to say they won't have a review.
"What impact does that have on a community? It's an absolute shambles."
Mr Robinson said if the Parades Commission continued to act in a "foolish" way it should be replaced.
Mr McGuinness then joined Sinn Féin president Gerry Adams and vice-president Mary Lou McDonald later in a separate meeting with Mr Cameron.
The UK leader had come under came for not meeting with the party since coming into office despite meeting with the DUP several times.
Speaking after the meeting, Sinn Féin president Gerry Adams said it had been "useful".
He went on: "The meeting provided the Sinn Féin leadership with an opportunity to express our serious concerns to Mr Cameron at his government's disconnect from its responsibilities under the terms of the Good Friday and other agreements.
"In our view the political process in the north of Ireland has deteriorated in recent months.
"Recently Mr Cameron has begun to indicate an awareness that the process is in difficulties. He did so again today.
"If he is serious about making progress then the British government has to defend the integrity of the Good Friday Agreement and engage positively with the process.
"This includes supporting the Haass compromise proposals and implementing outstanding issues arising from the Good Friday and other agreements."