Fighting in Afghanistan is intensifying between coalition forces and anti-government militants. Security concerns and logistical problems could force another delay to Afghanistan's national elections.

The U.S. military says two Afghan government soldiers and two U.S. Marines were wounded in an attack Tuesday, in Uruzgan province against fighters loyal to Afghanistan's former Taleban regime.

An interpreter working with the coalition was also injured in the fighting.

Afghan officials placed the number of Taleban killed at 21, although a U.S. spokesman said only that a "substantial number" were killed and one militant was taken prisoner.

Tuesday's engagement was initiated by coalition troops, following a series of attacks against them by the Taleban. A U.S. military statement described Tuesday's assault as "ambushing the ambushers."

Coalition forces have suffered at least two bomb attacks since Monday, including one that took the life of a U.S. soldier - the 91st to die since the start of the 2001 war that drove the Taleban from power.

Another attack touched off a skirmish near the eastern city of Jalalabad on Monday.

The U.S. military has acknowledged a significant rise in the number of Taleban attacks in recent months and says they are meant to derail plans for Afghanistan's first post-war election later this year.

The elections were originally scheduled for this month, but were postponed until September due to a lack of security for election workers seeking to register voters.

On Wednesday, Lieutenant Colonel Tucker Mansager, the U.S. military spokesman, expressed confidence that coalition forces would be able to provide adequate security in areas where the Taleban still pose a threat.

"The coalition will provide an overall security framework throughout particularly the more contentious areas of the country, to allow the government of Afghanistan and the United Nations Assistance Mission to do their job in a safe and secure environment," he said.

But observers say security issues have slowed voter registration to the point that the election date may have to be delayed yet again.

Afghan authorities and U.N. workers have so far registered about one third of the 10.5 million eligible Afghan voters.

With new registrations running at less than 30,000 per day, the election authorities may prove unable to process enough voters to hold a credible election by September.

Under a newly passed Afghan law, the country's independent election commission must announce the date for voting at least 90 days in advance, giving it until the end of this month to meet the September deadline.

Pakistan, meanwhile, has also been conducting operations against suspected foreign militants on its territory, who are believed to be conducting cross-border attacks on Afghan targets. Pakistan said a clash with suspected insurgents Wednesday left at least seven such fighters dead.