ABUJA (Reuters) - U.S. Secretary of State John Kerry made "very strong commitments" on ways to ramp up military assistance to help Nigeria defeat the extremist group Boko Haram, a senior U.S. official said on Tuesday.

In talks with Nigerian President Muhammadu Buhari, Kerry "made very, very strong commitments to the government that we are going to look at what we can do differently," the official said, adding that Kerry had told his staff to look at ways to boost military cooperation with Nigeria.

The official said Kerry had stressed that more needed to be done in working with neighbouring countries, as well as Britain and France, "so we can ramp up and bring this fight to closure."

The U.S. is currently considering the sale of attack aircraft to Nigeria, which is subject to review by Congress.

"We have been working with them to make sure they can afford it, and they know how to use it," the official said.

The official said a large part of the conversation during the one-hour meeting at the presidential villa in Abuja was dedicated to ways of boosting economic growth in Nigeria.

Nigeria is in the middle of its worst economic slump in decades. Falling oil revenues have hit public finances and the value of the naira, Nigeria's currency.

The United States has long pushed Nigeria to loosen its grip on the currency to help boost private investment.

"It was a huge topic," the official said of the discussions about the economy during the meeting. The U.S. has previously offered to send experts to work with Nigeria's treasury.

"The Secretary made offers to provide additional assistance on the economy," the official added.

Buhari noted during the talks that the situation in the Niger River Delta, where Nigeria faces violent unrest from local militants, was "making it hard for the government to continue to address the broader problems."