Prime Minister Stephen Harper will discuss economic reform measures with his Liberal rival in an attempt to defuse a brewing political showdown which threatens to spark a summer election.

Harper invited Liberal Leader Michael Ignatieff to his office for a Tuesday meeting, and Ignatieff agreed.

"I am always willing to meet with someone," Harper said in Ottawa on Monday, responding to opposition demands the government alter Employment Insurance and the stimulus program by the end of the week in order to avoid an election.

Still, Harper said the opposition's proposal to lower EI eligibility to 360 hours - a figure equal to only 45 workdays - is "irresponsible."

Instead, Harper said he is open to extending EI benefits to self-employed workers not currently covered under EI. But Harper stressed that reforming EI is a complicated issue that "cannot be done on the back of an envelope in a few days."

While Harper agreed to meet with Liberal Leader Michael Ignatieff, he urged the opposition to support the government's summer fiscal update on Friday in order to speed spending aimed at creating summer jobs.

"You can't say you're concerned about spending not happening, and then vote against giving the government the authority to spend money," Harper said, responding to opposition accusations that the government has been slow to roll out the funds.

The opposition has threatened to topple the government over four issues: EI reform, stimulus spending, the growing deficit and the medical isotope shortage.

But Ignatieff appeared to take a step back on Monday afternoon.

Ignatieff also said he would go along with extending the current session of Parliament -- which is scheduled to end for summer break this Friday -- to deal with his quartet of demands.

"I'm not sticking to a Friday deadline, but I think we are coming to a crunch here," Ignatieff told CTV's Power Play, adding he's open to meeting with Harper.

"I'm willing to work with him if he's willing to work with me."

Still, Ignatieff said he still hasn't been given a straight answer about how much infrastructure spending has actually been pumped into the economy.

"That's a simple question, to which all I need is a simple answer."

Ignatieff spent the weekend poring over the economic report card that was presented by Harper last week, and speaking to his advisers. It was the second economic update provided by the Conservatives since they introduced the budget in January.

Harper is dragging his feet, says NDP

NDP Leader Jack Layton accused the Conservatives Monday of intentionally dragging their feet on stimulus spending in order to keep the money in Ottawa's coffers.

"The fact is, Stephen Harper doesn't really believe in all this stimulus stuff," Layton told reporters, adding that Harper only implemented the spending because of opposition pressure.

Layton said that municipalities across the country "are starving" and the Tories have only pledged "crumbs" to help create summer construction jobs.

"It doesn't look as though he intends to follow through ... That's our problem with the budget."

The New Democrats and Bloc Quebecois already vowed they will vote against spending estimates that will come before Parliament as a confidence motion on Friday. After Ignatieff made his announcement on Monday, representatives of both parties indicated they hadn't changed their position.

Bloc Leader Gilles Duceppe said he disagreed with the original budget and last week's update, and called Ignatieff's position "lukewarm."

NDP deputy leader Thomas Mulcair also said he would be voting against the spending estimates.

If both the Bloc and NDP reject the spending estimates on Friday, it will be up to the Liberals to support it, or accept that the government will fall and an election will be triggered.

Ahead of Ignatieff's announcement, Transport Minister John Baird warned the Conservatives would not be bullied into making changes to EI, suggesting a Liberal ultimatum on the issue would likely result in an election.

Ignatieff's announcement stopped well short of doing that, said Tom Clark, host of Power Play.

"I think Michael Ignatieff took a big stick and drew a line in the sand. And then he took that stick and erased parts of the line big enough that you could drive a prime-ministerial limousine through. Look, there's not going to be an election over this."