MEXICO CITY (AFP) - Former US secretary of state Hillary Clinton said on Friday she would likely decide whether she will join the 2016 presidential race early next year.

Mrs Clinton, who lost the Democratic presidential nomination to Barack Obama in 2008, is widely expected to make another run for the White House.

"I will be making a decision around probably after the first of the year about whether I am going to run again or not," the former first lady said in Mexico City at a forum hosted by the Telmex Foundation of Mexican billionaire Carlos Slim.

"It's a very serious undertaking, so obviously I'm thinking about it, but I have not made a decision yet," said Mrs Clinton, who has previously indicated she would not make an announcement this year.

She was speaking just as a potential rival in the 2016 election, New Jersey's Republican Governor Chris Christie, wrapped up a three-day visit to Mexico to burnish his foreign policy credentials.

Mr Christie met Mexican President Enrique Pena Nieto earlier in the week, while Clinton held talks with the Latin American leader on Friday.

At the Telmex event, Mrs Clinton said her experiences as first lady, senator and secretary of state have given her a "unique vantage point" about "what makes the United States operate well and what doesn't, and what a president can do and should be doing." Speaking to 10,000 young Mexicans who have received Telmex Foundation scholarships, Clinton shared her life experiences but also briefly touched on world affairs, voicing concern about Russia's role in the Ukraine conflict.

"I do worry about President Putin's view that Russia should dominate its borders and intimidate people beyond its borders, using gas and oil as a weapon even, as we are seeing now with Ukraine, military force," she said.

"It is very important that Europe remain whole, stable and at peace and that Russia be persuaded or somehow convinced, even coerced, into looking toward the future, not the past," said Mrs Clinton, who served as the top US diplomat during Mr Obama's first term between 2009-2013.

Before her appearance, Ukraine and pro-Moscow rebels signed a ceasefire agreement in Minsk, raising hopes for an end to the five-month war that has left about 2,600 people dead.

Mr Obama, speaking at the end of a Nato summit in Wales, said US and European Union sanctions against Russia over the crisis would likely remain in place despite the ceasefire, but could be lifted if the truce holds.