T-Mobile, owned by Deutsche Telekom AG, said the software was available for users to download to their iPhones on Tuesday, but that it was not yet clear if the upgrade would fix all the connection problems.

"We have had complaints about connectivity in the Netherlands but have not had more complaints than usual for a 3G phone in Germany. Our technicians said today Apple has issued a software update but it is too early to tell if the problems are solved," a T-Mobile spokesman said.

AT&T Inc the only US network operator carrying the iPhone, confirmed that Apple had provided a software update but declined to give details about what it was aimed at fixing.

Apple, which sold about a million iPhones around the launch weekend in July, was not immediately available for comment.

Credit Suisse said in a note on Tuesday that iPhone sales could exceed 2 million units in the United States in the third quarter, which is roughly twice the sales of the iPhone's version 1.0, the initial release last year. That would be consistent with AT&T comments, Credit Suisse added.

One of the key attractions of the latest iPhone is its faster, third-generation (3G) Web connections when compared with the first iPhone that was launched in mid-2007.

However, users around the world have complained about dropped calls and inconsistent Internet speeds, with the phone often reverting to a slower technology known as Edge even in 3G areas.

Nomura analyst Richard Windsor and media reports have blamed faulty software on an Infineon Technologies AG chip for the problems. Infineon declined to comment about iPhone but said its chips work on 3G phones from suppliers such as Samsung Electronics Co without problems.