Baghdad ? A top U.S. military spokesman in Iraq said Sunday that the use of a lethal roadside bomb thought to come from Iran declined last week after a sharp increase earlier this month.

Ten days ago, Gen. David Petraeus, the top U.S. military commander in Iraq, noted a sharp rise in the use of explosively formed penetrators. The sophisticated roadside bombs, which fire slugs of metal that can pierce even the most robust armor, are thought to come from Iran and have killed hundreds of U.S. soldiers.

At a news conference Sunday, Rear Adm. Gregory Smith said the use of EFPs has returned to “normal levels” after a brief increase in the first weeks of January. He couldn’t explain the increase, nor could he say if Iran was behind the delivery of the weapons to Iraq.

Smith, however, said there’s evidence that Iran continues to train and support Iraqi Shiite Muslim groups.

“We continue to see a negative influence by Iran,” Smith said. “We clearly see their intent of training and financing continues.”

Tensions between the Bush administration and Iran remain high. During his Mideast trip this month, President Bush declared, “Iran is a threat,” and his administration and the U.S. military have accused Iran’s Islamic Revolutionary Guard Corps and its Quds Force of training and equipping Iraqi Shiite militias that attack U.S. soldiers.

Over the past two months, however, U.S. military officials in Iraq have said, the Iranians have smuggled fewer weapons into Iraq, although the officials have said they aren’t sure how to explain the decline.

Sunday’s news conference, which summarized the U.S.-led coalition’s efforts against al-Qaida in Iraq in the past year, was held as a teenage suicide bomber killed the leader of a Sunni group allied with the U.S. near Fallujah. The so-called awakening councils, predominantly Sunni, have been a key part of the U.S. strategy against Sunni Islamic extremists in the past year, and there have been increased attacks on them in recent weeks.

Smith also said that nearly half of the foreign insurgents in Iraq come from Saudi Arabia, which President Bush visited on his trip. Other foreign fighters have come from Libya, Yemen, Syria, and even a few from France, Smith said.

In the last year, improved border enforcement by Syria and increased profiling by Saudi officials of single males traveling to Iraq have helped cut the number of foreign fighters entering Iraq in half, Smith said. Between 40 and 50 a month are thought to be entering Iraq now, he said.

Between 50 percent and 60 percent of those become suicide bombers, and 90 percent of the suicide bombers are thought to be foreigners.