Apple has acknowledged that holding the iPhone 4 may result in a diminished signal that could make it difficult to make and maintain calls or retain a data connection.

"Gripping any phone will result in some attenuation of its antenna performance with certain places being worse than others depending on the placement of the antennas. This is a fact of life for every wireless phone," Apple said in a statement issued to several media outlets, including PC Magazine, which had run tests yesterday. "If you ever experience this on your Phone 4, avoid gripping it in the lower left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases."

Apple's iPhone 4 signal problems have been the source of a barrage of complaints by customers complaining of a faulty antenna and now Steve Jobs has broken the silence. In an e-mail Jobs downplayed users' reception gripes as a "non-issue." Meanwhile, others within Apple are advising iPhone 4 users to avoid gripping the device from the lower left corner.

As the first batch of iPhone 4 smartphones reached the market on Thursday, several users reported that they are having poor reception issues with their new device when holding the phone by its metal sides in two opposite places.

The metal bands surrounding the sides of the iPhone 4 also acts as antennas for the device, and the signal drop problem seems to appear when a user touches both of the black lines on the phone's metal sides towards the bottom, according to corroborated users reports.

"Gripping any phone will result in some attenuation of its antenna performance, with certain places being worse than others depending on the placement of the antennas. This is a fact of life for every wireless phone," reads an official Apple statement on Thursday.

"If you ever experience this on your iPhone 4, avoid gripping it in the lower left corner in a way that covers both sides of the black strip in the metal band, or simply use one of many available cases," the statement concludes.

Jobs also replied to a few complaints sent to his e-mail inbox. One MacRumors reader asked Jobs what is going to be done about the signal dropping issue, and the Apple CEO replied in his typical brief manner: "Non issue. Just avoid holding it in that way."

Spencer Webb, an antenna designer, explains on his blog that the iPhone 4 has two symmetrical slots in the metal frame, which when covered, will affect antenna performance. "There is no way around this, it's a design compromise that is forced by the requirements of the FCC, AT&T, Apple's marketing department and Apple's industrial designers, to name a few," Webb wrote.

Apple currently sells a $29 rubber "Bumper Case" for the iPhone 4 (pictured above), which covers only the sides of the device, something that made Mashable's Barb Dybwad ask whether this indicates that Apple already knew about the potential reception issues with the phone.

PCWorld also did its own tests of iPhone 4 signal and took the new phone for a spin in San Francisco alongside an iPhone 3GS. PCWorld was able to replicate the signal problems when covering the bottom left edge of the phone, something that did not occur when the phone was laid flat on a table with the antenna untouched.

The iPhone 4 particularly affects users that hold the phone in their left hand. "That's certainly possible," said Aaron Vronko, CEO of Rapid Repair, a US repair firm and do-it-yourself parts supplier for the iPhone, iPod and iPad  Vronko, who regularly takes apart Apple hardware to get an idea of how they're built and their capabilities, completed a teardown of the iPhone 4 by early Thursday, just hours before the smartphone went on sale at Apple's US retail stores.

As Vronko explained it, holding the iPhone 4 in a specific way could disrupt one or more of the two antennas embedded in the steel strip running along the outside edge of the case. "Holding it, especially if your skin was a little bit sweaty, could bridge one or more of the antennas," said Vronko. "That would change the length of the antenna, so it would be tracking a different wavelength than Apple designed it for."

As Apple noted in its statement, the problem could pop up for any mobile phone. But Vronko maintained that the iPhone 4 - which places the two antenna on the outside of the case, as opposed to inside, as was their location in the earlier iPhone 3G and 3GS - could be especially susceptible to the signal degradation.

"We are, after all, water-filled creatures," said Vronko, "and it's a fact that water affects radio signals. But the length of those antennas has to be a precise to capture the desired band of energy".

The left-handedness of the reception problem also has some foundation in fact. The antenna on the left side of the iPhone handles Wi-Fi and Bluetooth signals, while the one on the right receives cellular signals. Holding the iPhone 4 in the left hand would put more skin - all four fingers - in contact with the right side of the case.

Vronko said Rapid Repair is preparing to test the ability of the iPhone 4 to obtain and maintain a cellular signal, and would release its data as soon as it completes its investigation.

After stripping down the iPhone 4 into its component parts, Vronko's impression was mostly favourable. "It's significantly more rigid," he said, referring to the glass back and steel band that replaced plastic components in the previous models. "It should be able to absorb more shock."

But he wasn't ready to say that the new iPhone would be problem free. "I think it will have a less minor damage [to] it over time, but a little more chance of major damage if it's dropped and the glass back breaks."

Gregg Keizer from Computerworld contributed to this report