Harper told journalists Wednesday in London that his government will only agree to a deal when it meets Canada's best interests.
"Obviously, these have been long discussions. They're continuing. We have been making a lot of progress, and they are the biggest trade negotiations Canada has ever had in its history," the prime minister said.
"That said — and you know, obviously this will be a big discussion this week — but obviously, that said, we are not going to set a timeline or a fixed date on which we're going to have an agreement, because it is essential that we be driven by the contents of the discussions.
"We will not arrive at an accord until such time as we think we have the best accord we can get for the Canadian people. And that will be what drives us, the contents, not some artificial timeline."
He says Canada has made a lot of progress on the talks, and expects those discussions to continue while he is in Europe this week.
Canada is under pressure to conclude a deal before the European Union turns its attention to free trade negotiations with the United States this summer.
Among the issues believed to be on the negotiating table are financial services, Canadian beef exports, country-of-origin rules for vehicles, procurement limits for provinces and municipalities and drug patent protection.
Harper is in London until Thursday, when he leaves for Paris followed by Dublin before joining other G8 leaders in Northern Ireland for their annual summit.