Iraq’s beleaguered military launched an offensive against Sunni extremists in the northern city of Tikrit, as a shipment of Russian military jets arrived in the country that could give the armed forces a tactical edge going forward.

While the bloody sectarian conflict rages on, President Obama said the Islamic State of Iraq and the Levant is attracting radicalized militants in both Iraq and Syria who could pose a threat to the United States.

“They are gaining strength in some places. We have seen Europeans who are sympathetic to their cause traveling into Syria, and now may travel into Iraq, getting battle-hardened. Then, they come back. They have got European passports. They do not need a visa to get into the United States,” said Obama, speaking on ABC This Week program.

The situation calls for preemptive measures, according to Republican Congressman Peter King.

“[Obama] should be very aggressive on this. Syria is our biggest threat right now, because not only are there thousands of Europeans who have visas to enter the United States, going to Syria, there are also at least 100 or so Americans who are over there in Syria right now. So, any of these people can go back to the United States and carry out the type of attack that they are being trained in, in Syria,” said King.

The United States stands ready to act, according to President Obama.

“We are spending a lot of time, and we have been for years, making sure that we are improving intelligence so we can respond to that [threat]. We have to improve our surveillance, reconnaissance and intelligence there. Special forces are going to have a role [to play], and there are going to be times where we take strikes against organizations that could do us harm,” said Obama.

Heightened security measures are expected to be on display later this week during the July 4 Independence Day holiday.