Final bragging rights as the world's top carmaker - a title GM has held for 76 years - will not be decided until global vehicle production numbers get tallied for the full year.
But Tuesday's data show that Toyota is on track to overtake its American rival.
The Japanese company sold 2.35m vehicles worldwide in the first quarter, Toyota said, surpassing the 2.26m vehicles GM said it sold, according to preliminary figures.
In 2006, Toyota's global output rose 10 per cent to 9.018m vehicles, while GM and its affiliates produced 9.18m vehicles worldwide - a gap of about 162,000.
In the first quarter, Toyota made 2.37m units while GM had expected to produce 2.34m and has not given a final number.
Analysts say Toyota is building on its lead by investing in ecological technology, opening plants around the world, developing new models and wooing drivers with solid marketing that drives home its brand power.
Those are precisely areas in which GM has fallen behind, they say.
Koji Endo, an auto analyst with Credit Suisse in Tokyo, said Toyota sales were "booming because of its good image around the world about reliability and ecological technology".
"It's just the opposite for GM, and its image is deteriorating," he said.
"We also had a record first quarter globally. We set sales records in three out of our four regions. We're going to fight for every sale"
John McDonald, General Motors
But GM said that although Toyota had won the first quarter, the fight for global leadership for the year was not over.
A company spokesman said it would not chase market share solely to recapture the lead from Toyota, and it had no special plan to retake the lead.
"We also had a record first quarter globally. We set sales records in three out of our four regions," spokesman John McDonald said.
"We're going to fight for every sale."
Endo said that as Toyota got bigger, there might be problems.
"As your volume gets bigger and bigger, in many cases efficiency tends to drop. There might be a risk of being over-stretched."
Toyota has beaten GM in profitability for the past four years, with $11.8bn profit for the fiscal year to March 2006.
GM, meanwhile, has been negotiating severance packages with thousands of workers in an effort to turn around its North American operations.
In the fourth quarter of 2006, it reported a profit of $950m, a big turnaround from a loss of $6.6bn a year ago.