US President George W Bush has praised his Kazakh counterpart, Nursultan Nazarbayev, for transforming the former Soviet republic into a 'free nation'.
Mr Bush thanked Kazakhstan for its role in the "war on terror"
After talks between the two leaders in Washington, Mr Bush thanked his guest for backing US-led wars in Afghanistan and Iraq, and combating "extremism".
But economic ties between the US and oil-rich Kazakhstan topped the agenda.
US concerns over Kazakhstan's human rights record did not come up when the two leaders appeared before reporters.
In Kazakhstan, the media is controlled by the state and since the country achieved independence in December 1991 no election has been seen as free or fair.
The BBC's Jonathan Beale in Washington says the US has been willing to overlook complaints about Mr Nazarbayev's autocratic rule.
In a recent BBC interview, the Kazakh president agreed there may be a lack of democracy, but described political freedom as his goal and said the young country needed more time.
Kazakhstan is the closest US ally in central Asia.
Mr Bush thanked Mr Nazarbayev for his role in what Washington calls the war on terror, and its help with the post-war reconstruction of Iraq and Afghanistan.
The Kazakh leader was also praised for his "commitment to institutions that will enable liberty to flourish", and for developing his country into "a free nation".
For his part, Mr Nazarbayev said: "In economics, in energy partnership, in war on terror, we truly become close partners."
Following the "closed-door" talks, the leaders issued a joint statement saying the two countries' energy partnership would help US companies play a role in exploring Kazakhstan's vast oil and gas reserves around the Caspian Sea.
The US is the largest investor in Kazakhstan's oil and gas industry, and rivalry over its natural resources has turned the economy into a rare post-Soviet success story.
Analysts say that Kazakhstan is seen as an important new energy source for the West which could help reduce reliance on Middle Eastern oil.
Kazakhstan is expected to pump 3.5m barrels of oil a day in the coming decade. Both China and Russia are operating pipelines in the country.
Kazakhstan's dismantling of its nuclear arsenal after the collapse of the Soviet Union also pleased Washington, our correspondent says.