KABUL, Afghanistan — Diplomats from the United States and Afghanistan met formally Saturday for just the second time since the two countries signed a Strategic Partnership Agreement a year ago as they sought to hammer out a pact defining Washington's 10-year commitment to the war-ravaged country.

A senior diplomat from each nation spoke of progress afterward, but the talks come at a time of tension over Afghan President Hamid Karzai's criticism of U.S. actions in his country as the NATO combat mission winds down.

The Afghan president has accused the U.S. of colluding with the Taliban and scheming to back his political opponents. In a speech here Thursday, Karzai revealed confidential details of U.S.-Afghan security talks, saying that Washington was seeking the use of nine military bases in Afghanistan after 2014, when the Western combat mission is scheduled to end.

U.S. Deputy Secretary of State William J. Burns emphasized in remarks before Saturday's session that Washington was not backing any candidate to replace Karzai in national elections, set for April 2014.

"We are supporting the process and not any particular candidate," Burns told reporters at the Afghan Ministry of Foreign Affairs. He said the election should be "transparent, credible and inclusive."

Burns reaffirmed the long-term American commitment to Afghanistan, saying, "As the Afghan people stand up, you will not stand alone."

The U.S. has pledged diplomatic, economic and security support after North Atlantic Treaty Organization troops leave. But details have yet to be worked out, with the U.S. seeking to curb rampant Afghan government corruption and demanding a commitment to political freedom and human rights, particularly the rights of women and girls.

Afghan Foreign Minister Zalmai Rassoul described "substantial progress" on the security front, saying that 90% of the population lives in areas where Afghan forces have taken over the lead from U.S. and coalition forces in the fight against the Taliban and other insurgents.

Burns said the U.S. was on schedule to transfer all security and combat responsibilities to Afghan forces by the end of the year. U.S. forces, now numbering about 63,000, will be reduced by half by early next year under a timetable announced by President Obama. The troops are completing a transition from combat to training and advising the Afghan army and police.

In a joint statement Saturday, the two sides said they were committed to job creation, economic growth and improved infrastructure for Afghanistan. The statement said the talks are intended the lay the groundwork for a "sovereign, unified and democratic Afghanistan," with "respect for human rights, the rule of law and democratic values."

Burns said the United States is committed to peace talks in Doha, Qatar, between the Afghan government's High Peace Council and Taliban representatives. But the effort has stalled, with the Taliban refusing to negotiate with the Karzai government, which it calls a "stooge regime."

The Strategic Partnership Agreement was signed here in May 2012 by Karzai and Obama. The two sides first met in Washington in October, with the next meeting scheduled there this October.

Separately, the two countries are negotiating a bilateral security agreement on the presence of any U.S. troops who will serve in Afghanistan after 2014. The number of troops will be decided by Obama, with the U.S. seeking to deny Al Qaeda and its affiliates a foothold in Afghanistan.

Also Saturday, Afghan officials reported that 11 Afghans working for a United Nations-affiliated mine-clearing agency had been abducted Thursday.

Hazrat Hussain Mashreqiwal, a police spokesman in the eastern province of Nangarhar, told The Times in a telephone interview that the mine-clearing workers and their drivers were seized in the remote Achin district by Taliban insurgents. Local district officials and village elders in the area were trying to negotiate the men's release, he said.

Meanwhile, officials in Farah province, in western Afghanistan, said Iranian border guards had opened fire Friday on Afghans attempting to cross illegally into Iran, killing 10 and wounding nine. Mohammed Younus Rafouli, deputy provincial governor, told The Times that the Afghans had paid smugglers to help them cross the border without documents.

Thousands of Afghans have sought to enter Iran in search of jobs and safety.

Rafouli said he had no information on why the Iranians would have opened fire on unarmed civilians. More than 100 Afghans attempted to cross the border during the incident, he said. Three smugglers were arrested by provincial police.

The Iranian Embassy in Kabul did not respond to requests for comment Saturday.

Special correspondent Hashmat Baktash contributed to this report.

david.zucchino@latimes.com