US President Barack Obama has said he would not start "wheeling and dealing" with China and Russia over a US request to extradite former American spy agency contractor and whistleblower Edward Snowden.

Speaking to reporters in Senegal's capital Dakar, where he started his three-country tour of Africa, Obama on Thursday said regular legal channels should suffice to handle the US request that Snowden, who left Hong Kong for Moscow, be returned.

Obama said he had not yet spoken to China's President Xi Jinping or Russian President Vladimir Putin on the issue.

"The reason is ... number one, I shouldn't have to. Number two, we've got a whole lot of business that we do with China and Russia, and I'm not going to have one case of a suspect who we're trying to extradite suddenly being elevated to the point where I've got to start doing wheeling and dealing and trading on a whole host of other issues," the US President said.

Obama also dismissed suggestions that the US might try to intercept Snowden if he were allowed to depart Moscow by air and said he is not going to be "scrambling jets to get a 29-year-old hacker".

The US has been seeking Snowden's custody since he leaked details of secret US government surveillance programmes.

Washington has annulled Snowden's passport and wants him returned to face espionage charges.

Snowden is believed to be hiding in the transit area of the Sheremetyevo airport near Moscow, the Russian capital.

Ecuador ignores US warning

Meanwhile, Ecuador has announced that it will renounce the trade benefits under a US trade agreement unilaterally to demonstrate its principled approach to the asylum request of Snowden.

State officials said on Thursday that the country will not be subject to pressure from Washington, after a senior US politician issued a strong warning to cut ties with Ecuador if that country takes Snowden in.

Speaking in a news conference in capital Quito, Communications Minister Fernando Alvarado said that Ecuador gives up, “unilaterally and irrevocably”, the said customs benefits.

In a deliberately cheeky touch from the leftist government of President Rafael Correa, Ecuador also offered a multimillion donation for human rights training in the US.

"What's more, Ecuador offers the United States economic aid of $23 million annually, similar to what we received with the trade benefits, with the intention of providing education about human rights," Alvarado added.

Quito’s reaction came after Robert Menendez, the chairman of the US Senate Foreign Relations Committee, said that he would seek to end the preferential treatment for goods if the South American nation offers political asylum to Snowden.

Richard Patino, the country's foreign minister, said on Wednesday during a state visit to Malaysia that it took two months for the country to make a decision in the case of Julian Assange, the founder of whistleblowing website Wikileaks, and that Snowden's case would take at least as long from the time the request was filed.