Russia is deploying nuclear-capable Tu-160 Blackjack bombers to Venezuela this week as part of an increasingly provocative pattern of bomber training flights, according to American defense officials.

At least two Blackjacks will fly from a strategic forces air base in Russia to Venezuela as part of a series of training exercises that will include long-range refueling, said officials familiar with Russian plans for the flight.

The bomber foray to South America will be Russia's seventh training flight for Blackjack bombers in the past three months.

Mark Schneider, a former Pentagon official and specialist on the Russian military, said Tu-160 flights are unusual and increasing.

"There were six announced Tu-160 flights of the ‘provocative' type during the last three months, which is a lot," Schneider said.

The most recent incident took place near Norway in late October when Tu-160s were shadowed by British and Norwegian jet fighters over the Barents Sea.

Additionally, Russian forces utilized both Tu-160 and Tu-95 bombers during a recent strategic nuclear forces drill, and the Defense Ministry announced that the recent Ocean Shield exercise in the Mediterranean involved Blackjacks that were described by the Russian defense ministry as involving undisclosed new tactics.

"The announced Tu-160 flight over the North Pole is also unusual as well as clearly aimed at us," Schneider said. In August, two Blackjacks flew to the North Pole.

The Pentagon is expected to closely monitor the Blackjacks because of their potential to fire nuclear-armed cruise missiles at U.S. targets. A Pentagon spokesman could not be reached for comment Sunday.

Russian President Vladimir Putin announced in January 2018 that the military is investing $2.8 billion to modernize the Tu-160 fleet with new engines and advanced avionics.

Putin recently stepped up threatening rhetoric against the United States following the announcement by the Trump administration that it will pull out of the 1987 Intermediate-range Nuclear Forces Treaty over Moscow's violations of the accord.

Russia used Tu-160s in Syria in firing long-range cruise missiles.

In March, Russian Deputy Defense Minister Yury Borisov announced the Tu-160, a supersonic jet that is the largest combat aircraft in the world, is undergoing a major upgrade and carries nuclear-tipped KH-55 cruise missiles, as well as conventional KH-555 and KH-101 conventional cruise missiles.

"We are going to … carry out deep modernization of the planes [that are currently] in service when only the fuselage would remain while all the avionics equipment and engines would be replaced," Borisov said.

"One cannot even compare the Tu-160 aircraft equipped with the X-55, X-555, and X-101 missiles and a plane that we are hoping to get by 2030 equipped with new air-delivered ordnance that would have completely different effective distance," Borisov added.

At least five upgraded Tu-160s are currently deployed, along with 11 older variants.

The Russians dispatched two Blackjacks to Venezuela in September 2008 as part of a training mission in support of Venezuela's leftist then-President Hugo Chavez.

The latest flights are expected to be similar to those in 2008, when the bombers conducted training flights over international waters near Venezuela.

Disclosure of the bomber flights comes as Venezuela is experiencing political and economic crisis under the regime of President Nicolas Maduro that has become increasingly dependent on Russia for aid.

Maduro visited Moscow last week and was promised an estimated $6 billion in investment pledges in the oil and mining sectors aimed at propping up the regime in Caracas and its collapsing economy.

Maduro said Moscow also promised to help modernize Venezuela's military.

Defense ministers from the two countries met in Moscow last week and agreed that Russian air force and naval forces would continue to use Venezuelan ports and airports.

Russian officials, however, played down expectations of a major bailout for Venezuela, the Financial Times reported Monday.

The Russian state oil company Rosneft previously lent $6 billion to Venezuela's state oil company PDVSA.

Russian presidential spokesman Dmitry Peskov last week declined to comment on the new aid package for Venezuela but said: "A whole range of issues related to bilateral co-operation has been discussed. There is no doubt that Russia will continue supporting Venezuela to one degree or another."

Russia has sought closer ties to the anti-U.S. regime in Venezuela in response to U.S.-led sanctions against Moscow for its annexation of Ukraine's Crimea.

Russian chief of the general staff, Gen. Valery Gerasimov, said recently that in response to U.S. missile defenses Russia will be upgrading its nuclear forces, including equipping its current strategic bombers by expanding their range of weapons.

"In the next several months I expect additional threats including more bomber provocations and possibly significant military action against Ukraine," Schneider said.

"Normally in December they release a lot of information about their plans for the nuclear Strategic Missile Force. I expect they will make this as threatening as possible. I believe there will be more provocative bomber flights."

Update 6:08 p.m.: Two of the bombers arrived at Venezuela’s Maiquetta Airport on Monday.