There was no word on casualties on Saturday, and US military officials could not immediately be reached for comment.
Al Qaida's wing in Iraq said its "martyrdom brigade" was behind the attack, according to a statement posted on a web site.
After the blast, US forces immediately closed off the highway, which links Iraq to Jordan, Aljazeera learned.
Meanwhile, three Iraqi police officers were killed and seven wounded in a bomb blast in the tense northern oil centre of Kirkuk on Saturday as they buried a colleague killed the previous day, the city's police chief said.
"Around 10:30 (0730 GMT), three policemen were killed and seven others wounded by a bomb in the centre of Kirkuk as the funeral cortege of a colleague killed the day before passed by," said General Turhan Yusuf.
On Friday, Shia demonstrators raised the Iraqi flag over Jordan's embassy after more than 2000 people marched through Baghdad demanding an apology for the alleged involvement of a Jordanian in a bombing that killed 125 people.
Friday's protest - the largest in a week of mounting anger - came two days after the leader of the clergy-backed United Iraqi Alliance claimed during Iraq's first National Assembly meeting that neighbouring Jordan was not doing enough to prevent fighters from slipping into Iraq.
Hundreds of protesters converged on the Jordanian embassy after Friday prayers at three Shia mosques around Baghdad. They burned Israeli and Jordanian flags and shouted slogans against Jordan's King Abd Allah II, such as "Take your embassy away. We do not want to see you!" and "There's no God but God, Abd Allah is the enemy of God!"
Three men in green camouflage, including one wearing a black balaclava, were later seen on an embassy roof raising an Iraqi flag on a makeshift flagpole. Another pole that previously held the Jordanian banner was bare.
The Shia protesters burned
Shia have staged smaller protests in recent days after the Iraqi government on Monday condemned celebrations allegedly held by the family of a Jordanian man suspected of carrying out a 28 February attack that killed 125 people in al-Hilla, 96km south of Baghdad. Nearly all the victims were Shia police and army recruits.
The Jordanian daily al-Ghad reported that Raid Mansur al-Banna carried out the attack. The paper later issued a correction, however, saying it was not known where in Iraq al-Banna carried out an assault.
"The Jordanian king must apologise to the people of al-Hilla and the people of Iraq," said Qasim Husain, a Shia cleric at the protest. "Blood money must be paid to the victims of al-Hilla."
Iraqi police and special forces gathered outside the embassy but failed to prevent demonstrators from reaching the building. The protesters later dispersed; no violence was reported.
A number of Iraqi politicians including interim Prime Minister Iyad Allawi have demanded explanations from the Jordanian government.
"The government condemns strongly any attack against the Iraqi people, in particular the hideous massacre of al-Hilla, which killed scores of innocent people"
Jordan government spokesperson
Jordanian government spokeswoman Asma Khadir said her country condemned all terrorism and reconfirmed Jordan's solidarity with the Iraqi people.
"The government condemns strongly any attack against the Iraqi people, in particular the hideous massacre of al-Hilla, which killed scores of innocent people," Khadir said. "We have put intensive measures to track those terrorists, and there is security coordination with Iraq to protect the borders of both countries."
The protesters' anger also seemed to have been fuelled by comments late last year by King Abd Allah, a Sunni, criticising the rising Shia power in war-ravaged Iraq.
In other developments, an Iraqi-Swedish politician kidnapped in Baghdad in January has been freed, Sweden's Foreign Ministry said on Friday.
Minas al-Yusifi, the leader of Iraq's Christian Democrats who had returned from exile in Sweden to re-establish the party, was held by the Iraqi Vengeance Battalion, Martyr al-Isawi Brigade.