The US embassy in Cairo has reopened after a week-long closure due to security concerns.
The US announced on Friday that it was reopening 18 of the 19 embassies closed following online "chatter" about security threats.
However, the US embassy in Yemen and the US consulate in Lahore, Pakistan, remain due to a "separate credible threat."
The US government says it will reopen 18 of the 19 embassies it recently closed in the Middle East and Africa on Sunday due to security threats.
However, the State Department said its embassy in Yemeni capital Sanaa will remain closed.
– State Department spokeswoman Jen Psaki
Our embassy in Sanaa, Yemen, will remain closed because of ongoing concerns about a threat stream indicating the potential for terrorist attacks emanating from Al Qaeda in the Arabian Peninsula.
The US will also keep its consulate in Lahore, Pakistan, shuttered, Psaki said, adding it closed on Thursday due to a "separate credible threat."
Three US drone strikes killed a total of 12 suspect al-Qaeda militants in Yemen today, a military official in the country said.
The attacks contribute to a total of eight in under two weeks.
Yemen is on high alert after authorities said they thwarted an al-Qaeda plot to target foreign embassies in the country.
US and UK embassy staff were withdrawn early this week.
A US drone attack killed at least six suspected al-Qaeda militants in Yemen this morning, officials said. The attack is the sixth drone strike in less than a fortnight.
Witnesses and local officials in Maared, a mostly desert region where militants have taken refuge, said the drone fired at two vehicles suspected of carrying militants at dawn this morning.
At least 20 suspected militants have been killed in the country since July 28, officials say.
Yemen says it has foiled a plot by al-Qaeda to seize two major oil and gas export terminals in the east of the country.
The announcement of the thwarted plot comes days after all Western embassies in Yemen were closed amid the continued threat of a terror attack.
Yemeni government spokesman, Rajeh Badi, said the plot involved blowing up oil pipelines and taking control of key cities and was uncovered with Western and Arab help.
US ally Yemen, one of the poorest Arab countries, is the base for Al Qaeda in the Arabian Peninsula and is one of the most active branches of the network founded by Osama bin Laden.
Appearing on NBC's The Tonight Show with Jay Leno, President Obama said the current security alert for US citizens, following intelligence an attack was due to occur in Yemen, was a reminder that "radical, violent extremism is still out there."
Asked how significant the threat was, he said:
"It's significant enough that we're taking every precaution. We had already done a lot to bolster embassy security around the world, but especially in the Middle East and North Africa, where the threats tend to be highest.
"Whenever we see a threat stream that we think is specific enough that we can take some specific precautions within a certain timeframe, then we do so.
It's a reminder that for all the progress we've made -- getting bin Laden, putting al Qaeda between Afghanistan and Pakistan back on its heels -- that this radical, violent extremism is still out there. [...] Even if we reinforce it, there are still vulnerabilities.
The Yemeni government says the decision by US and British embassies to withdraw staff from the Arab nation "undermines the exceptional cooperation" between Yemen and the international community in the fight against terrorism.
Tuesday's decision to evacuate staff from the Arabian peninsula "serves the interests of the extremists", a statement from the Yemeni embassy in Washington said.
The embassy said it understands the concern of foreign governments for their citizens but insisted Yemen had taken all precautions to ensure the security of foreign missions in the capital, Sanaa.
Professor Fawaz Gerges, Professor of International Relations at the London School of Economics, says despite evidence of a terror threat in the Middle East, there is little detail about specific targets or dates of a potential attack.
All British Embassy staff have now been withdrawn and all Western embassies in Yemen have been closed. A US transport plane left there this morning with US Embassy staff. And, 19 American embassies or consulates in the Arab world and across North Africa have been closed.
That is almost unprecedented in its scope since the September 11th attacks. What is the plot? We don't actually know but we think it was directed against embassies and ambassadors in Yemen itself and was partly as a result of a large number of al Qaeda members seen in the capital Sanaa.
It was also the result of intercepted communications between al Qaeda's leader Ayman al-Zawahiri and his number two, who is the leader of al Qaeda in Yemen. He apparently gave clear, distinct orders for an attack to begin.